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* writeback: fix uninitialized task_ratelimitWu Fengguang2011-11-071-4/+4
| | | | | | | | | | | In balance_dirty_pages() task_ratelimit may be not initialized (initialization skiped by goto pause), and then used when calling tracing hook. Fix it by moving the task_ratelimit assignment before goto pause. Reported-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
* Merge branch 'modsplit-Oct31_2011' of ↵Linus Torvalds2011-11-0638-36/+33
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux * 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits) Revert "tracing: Include module.h in define_trace.h" irq: don't put module.h into irq.h for tracking irqgen modules. bluetooth: macroize two small inlines to avoid module.h ip_vs.h: fix implicit use of module_get/module_put from module.h nf_conntrack.h: fix up fallout from implicit moduleparam.h presence include: replace linux/module.h with "struct module" wherever possible include: convert various register fcns to macros to avoid include chaining crypto.h: remove unused crypto_tfm_alg_modname() inline uwb.h: fix implicit use of asm/page.h for PAGE_SIZE pm_runtime.h: explicitly requires notifier.h linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h miscdevice.h: fix up implicit use of lists and types stop_machine.h: fix implicit use of smp.h for smp_processor_id of: fix implicit use of errno.h in include/linux/of.h of_platform.h: delete needless include <linux/module.h> acpi: remove module.h include from platform/aclinux.h miscdevice.h: delete unnecessary inclusion of module.h device_cgroup.h: delete needless include <linux/module.h> net: sch_generic remove redundant use of <linux/module.h> net: inet_timewait_sock doesnt need <linux/module.h> ... Fix up trivial conflicts (other header files, and removal of the ab3550 mfd driver) in - drivers/media/dvb/frontends/dibx000_common.c - drivers/media/video/{mt9m111.c,ov6650.c} - drivers/mfd/ab3550-core.c - include/linux/dmaengine.h
| * mm: fix implicit stat.h usage in dmapool.cPaul Gortmaker2011-10-311-0/+1
| | | | | | | | | | | | | | | | | | The removal of the implicitly everywhere module.h and its child includes will reveal this implicit stat.h usage: mm/dmapool.c:108: error: ‘S_IRUGO’ undeclared here (not in a function) Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
| * mm: Map most files to use export.h instead of module.hPaul Gortmaker2011-10-3130-30/+30
| | | | | | | | | | | | | | | | The files changed within are only using the EXPORT_SYMBOL macro variants. They are not using core modular infrastructure and hence don't need module.h but only the export.h header. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
| * mm: Add export.h for EXPORT_SYMBOL to active symbol exportersPaul Gortmaker2011-10-312-0/+2
| | | | | | | | | | | | | | | | | | | | These files were getting <linux/module.h> via an implicit include path, but we want to crush those out of existence since they cost time during compiles of processing thousands of lines of headers for no reason. Give them the lightweight header that just contains the EXPORT_SYMBOL infrastructure. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
| * mm: delete various needless include <linux/module.h>Paul Gortmaker2011-10-316-6/+0
| | | | | | | | | | | | | | | | There is nothing modular in these files, and no reason to drag in all the 357 headers that module.h brings with it, since it just slows down compiles. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
* | Merge branch 'writeback-for-linus' of ↵Linus Torvalds2011-11-063-154/+560
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux * 'writeback-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Add a 'reason' to wb_writeback_work writeback: send work item to queue_io, move_expired_inodes writeback: trace event balance_dirty_pages writeback: trace event bdi_dirty_ratelimit writeback: fix ppc compile warnings on do_div(long long, unsigned long) writeback: per-bdi background threshold writeback: dirty position control - bdi reserve area writeback: control dirty pause time writeback: limit max dirty pause time writeback: IO-less balance_dirty_pages() writeback: per task dirty rate limit writeback: stabilize bdi->dirty_ratelimit writeback: dirty rate control writeback: add bg_threshold parameter to __bdi_update_bandwidth() writeback: dirty position control writeback: account per-bdi accumulated dirtied pages
| * | writeback: Add a 'reason' to wb_writeback_workCurt Wohlgemuth2011-10-313-3/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This creates a new 'reason' field in a wb_writeback_work structure, which unambiguously identifies who initiates writeback activity. A 'wb_reason' enumeration has been added to writeback.h, to enumerate the possible reasons. The 'writeback_work_class' and tracepoint event class and 'writeback_queue_io' tracepoints are updated to include the symbolic 'reason' in all trace events. And the 'writeback_inodes_sbXXX' family of routines has had a wb_stats parameter added to them, so callers can specify why writeback is being started. Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Curt Wohlgemuth <curtw@google.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: trace event balance_dirty_pagesWu Fengguang2011-10-311-0/+22
| | | | | | | | | | | | | | | | | | | | | Useful for analyzing the dynamics of the throttling algorithms and debugging user reported problems. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: trace event bdi_dirty_ratelimitWu Fengguang2011-10-311-0/+2
| | | | | | | | | | | | | | | | | | It helps understand how various throttle bandwidths are updated. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: fix ppc compile warnings on do_div(long long, unsigned long)Wu Fengguang2011-10-111-8/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fix powerpc compile warnings mm/page-writeback.c: In function 'bdi_position_ratio': mm/page-writeback.c:622:3: warning: comparison of distinct pointer types lacks a cast [enabled by default] page-writeback.c:635:4: warning: comparison of distinct pointer types lacks a cast [enabled by default] Also fix gcc "uninitialized var" warnings. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: dirty position control - bdi reserve areaWu Fengguang2011-10-031-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Keep a minimal pool of dirty pages for each bdi, so that the disk IO queues won't underrun. Also gently increase a small bdi_thresh to avoid it stuck in 0 for some light dirtied bdi. It's particularly useful for JBOD and small memory system. It may result in (pos_ratio > 1) at the setpoint and push the dirty pages high. This is more or less intended because the bdi is in the danger of IO queue underflow. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: control dirty pause timeWu Fengguang2011-10-031-1/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The dirty pause time shall ultimately be controlled by adjusting nr_dirtied_pause, since there is relationship pause = pages_dirtied / task_ratelimit Assuming pages_dirtied ~= nr_dirtied_pause task_ratelimit ~= dirty_ratelimit We get nr_dirtied_pause ~= dirty_ratelimit * desired_pause Here dirty_ratelimit is preferred over task_ratelimit because it's more stable. It's also important to limit possible large transitional errors: - bw is changing quickly - pages_dirtied << nr_dirtied_pause on entering dirty exceeded area - pages_dirtied >> nr_dirtied_pause on btrfs (to be improved by a separate fix, but still expect non-trivial errors) So we end up using the above formula inside clamp_val(). The best test case for this code is to run 100 "dd bs=4M" tasks on btrfs and check its pause time distribution. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: limit max dirty pause timeWu Fengguang2011-10-031-2/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Apply two policies to scale down the max pause time for 1) small number of concurrent dirtiers 2) small memory system (comparing to storage bandwidth) MAX_PAUSE=200ms may only be suitable for high end servers with lots of concurrent dirtiers, where the large pause time can reduce much overheads. Otherwise, smaller pause time is desirable whenever possible, so as to get good responsiveness and smooth user experiences. It's actually required for good disk utilization in the case when all the dirty pages can be synced to disk within MAX_PAUSE=200ms. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: IO-less balance_dirty_pages()Wu Fengguang2011-10-031-105/+56
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As proposed by Chris, Dave and Jan, don't start foreground writeback IO inside balance_dirty_pages(). Instead, simply let it idle sleep for some time to throttle the dirtying task. In the mean while, kick off the per-bdi flusher thread to do background writeback IO. RATIONALS ========= - disk seeks on concurrent writeback of multiple inodes (Dave Chinner) If every thread doing writes and being throttled start foreground writeback, it leads to N IO submitters from at least N different inodes at the same time, end up with N different sets of IO being issued with potentially zero locality to each other, resulting in much lower elevator sort/merge efficiency and hence we seek the disk all over the place to service the different sets of IO. OTOH, if there is only one submission thread, it doesn't jump between inodes in the same way when congestion clears - it keeps writing to the same inode, resulting in large related chunks of sequential IOs being issued to the disk. This is more efficient than the above foreground writeback because the elevator works better and the disk seeks less. - lock contention and cache bouncing on concurrent IO submitters (Dave Chinner) With this patchset, the fs_mark benchmark on a 12-drive software RAID0 goes from CPU bound to IO bound, freeing "3-4 CPUs worth of spinlock contention". * "CPU usage has dropped by ~55%", "it certainly appears that most of the CPU time saving comes from the removal of contention on the inode_wb_list_lock" (IMHO at least 10% comes from the reduction of cacheline bouncing, because the new code is able to call much less frequently into balance_dirty_pages() and hence access the global page states) * the user space "App overhead" is reduced by 20%, by avoiding the cacheline pollution by the complex writeback code path * "for a ~5% throughput reduction", "the number of write IOs have dropped by ~25%", and the elapsed time reduced from 41:42.17 to 40:53.23. * On a simple test of 100 dd, it reduces the CPU %system time from 30% to 3%, and improves IO throughput from 38MB/s to 42MB/s. - IO size too small for fast arrays and too large for slow USB sticks The write_chunk used by current balance_dirty_pages() cannot be directly set to some large value (eg. 128MB) for better IO efficiency. Because it could lead to more than 1 second user perceivable stalls. Even the current 4MB write size may be too large for slow USB sticks. The fact that balance_dirty_pages() starts IO on itself couples the IO size to wait time, which makes it hard to do suitable IO size while keeping the wait time under control. Now it's possible to increase writeback chunk size proportional to the disk bandwidth. In a simple test of 50 dd's on XFS, 1-HDD, 3GB ram, the larger writeback size dramatically reduces the seek count to 1/10 (far beyond my expectation) and improves the write throughput by 24%. - long block time in balance_dirty_pages() hurts desktop responsiveness Many of us may have the experience: it often takes a couple of seconds or even long time to stop a heavy writing dd/cp/tar command with Ctrl-C or "kill -9". - IO pipeline broken by bumpy write() progress There are a broad class of "loop {read(buf); write(buf);}" applications whose read() pipeline will be under-utilized or even come to a stop if the write()s have long latencies _or_ don't progress in a constant rate. The current threshold based throttling inherently transfers the large low level IO completion fluctuations to bumpy application write()s, and further deteriorates with increasing number of dirtiers and/or bdi's. For example, when doing 50 dd's + 1 remote rsync to an XFS partition, the rsync progresses very bumpy in legacy kernel, and throughput is improved by 67% by this patchset. (plus the larger write chunk size, it will be 93% speedup). The new rate based throttling can support 1000+ dd's with excellent smoothness, low latency and low overheads. For the above reasons, it's much better to do IO-less and low latency pauses in balance_dirty_pages(). Jan Kara, Dave Chinner and me explored the scheme to let balance_dirty_pages() wait for enough writeback IO completions to safeguard the dirty limit. However it's found to have two problems: - in large NUMA systems, the per-cpu counters may have big accounting errors, leading to big throttle wait time and jitters. - NFS may kill large amount of unstable pages with one single COMMIT. Because NFS server serves COMMIT with expensive fsync() IOs, it is desirable to delay and reduce the number of COMMITs. So it's not likely to optimize away such kind of bursty IO completions, and the resulted large (and tiny) stall times in IO completion based throttling. So here is a pause time oriented approach, which tries to control the pause time in each balance_dirty_pages() invocations, by controlling the number of pages dirtied before calling balance_dirty_pages(), for smooth and efficient dirty throttling: - avoid useless (eg. zero pause time) balance_dirty_pages() calls - avoid too small pause time (less than 4ms, which burns CPU power) - avoid too large pause time (more than 200ms, which hurts responsiveness) - avoid big fluctuations of pause times It can control pause times at will. The default policy (in a followup patch) will be to do ~10ms pauses in 1-dd case, and increase to ~100ms in 1000-dd case. BEHAVIOR CHANGE =============== (1) dirty threshold Users will notice that the applications will get throttled once crossing the global (background + dirty)/2=15% threshold, and then balanced around 17.5%. Before patch, the behavior is to just throttle it at 20% dirtyable memory in 1-dd case. Since the task will be soft throttled earlier than before, it may be perceived by end users as performance "slow down" if his application happens to dirty more than 15% dirtyable memory. (2) smoothness/responsiveness Users will notice a more responsive system during heavy writeback. "killall dd" will take effect instantly. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: per task dirty rate limitWu Fengguang2011-10-031-39/+50
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add two fields to task_struct. 1) account dirtied pages in the individual tasks, for accuracy 2) per-task balance_dirty_pages() call intervals, for flexibility The balance_dirty_pages() call interval (ie. nr_dirtied_pause) will scale near-sqrt to the safety gap between dirty pages and threshold. The main problem of per-task nr_dirtied is, if 1k+ tasks start dirtying pages at exactly the same time, each task will be assigned a large initial nr_dirtied_pause, so that the dirty threshold will be exceeded long before each task reached its nr_dirtied_pause and hence call balance_dirty_pages(). The solution is to watch for the number of pages dirtied on each CPU in between the calls into balance_dirty_pages(). If it exceeds ratelimit_pages (3% dirty threshold), force call balance_dirty_pages() for a chance to set bdi->dirty_exceeded. In normal situations, this safeguarding condition is not expected to trigger at all. On the sqrt in dirty_poll_interval(): It will serve as an initial guess when dirty pages are still in the freerun area. When dirty pages are floating inside the dirty control scope [freerun, limit], a followup patch will use some refined dirty poll interval to get the desired pause time. thresh-dirty (MB) sqrt 1 16 2 22 4 32 8 45 16 64 32 90 64 128 128 181 256 256 512 362 1024 512 The above table means, given 1MB (or 1GB) gap and the dd tasks polling balance_dirty_pages() on every 16 (or 512) pages, the dirty limit won't be exceeded as long as there are less than 16 (or 512) concurrent dd's. So sqrt naturally leads to less overheads and more safe concurrent tasks for large memory servers, which have large (thresh-freerun) gaps. peter: keep the per-CPU ratelimit for safeguarding the 1k+ tasks case CC: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Andrea Righi <andrea@betterlinux.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: stabilize bdi->dirty_ratelimitWu Fengguang2011-10-032-1/+71
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are some imperfections in balanced_dirty_ratelimit. 1) large fluctuations The dirty_rate used for computing balanced_dirty_ratelimit is merely averaged in the past 200ms (very small comparing to the 3s estimation period for write_bw), which makes rather dispersed distribution of balanced_dirty_ratelimit. It's pretty hard to average out the singular points by increasing the estimation period. Considering that the averaging technique will introduce very undesirable time lags, I give it up totally. (btw, the 3s write_bw averaging time lag is much more acceptable because its impact is one-way and therefore won't lead to oscillations.) The more practical way is filtering -- most singular balanced_dirty_ratelimit points can be filtered out by remembering some prev_balanced_rate and prev_prev_balanced_rate. However the more reliable way is to guard balanced_dirty_ratelimit with task_ratelimit. 2) due to truncates and fs redirties, the (write_bw <=> dirty_rate) match could become unbalanced, which may lead to large systematical errors in balanced_dirty_ratelimit. The truncates, due to its possibly bumpy nature, can hardly be compensated smoothly. So let's face it. When some over-estimated balanced_dirty_ratelimit brings dirty_ratelimit high, dirty pages will go higher than the setpoint. task_ratelimit will in turn become lower than dirty_ratelimit. So if we consider both balanced_dirty_ratelimit and task_ratelimit and update dirty_ratelimit only when they are on the same side of dirty_ratelimit, the systematical errors in balanced_dirty_ratelimit won't be able to bring dirty_ratelimit far away. The balanced_dirty_ratelimit estimation may also be inaccurate near @limit or @freerun, however is less an issue. 3) since we ultimately want to - keep the fluctuations of task ratelimit as small as possible - keep the dirty pages around the setpoint as long time as possible the update policy used for (2) also serves the above goals nicely: if for some reason the dirty pages are high (task_ratelimit < dirty_ratelimit), and dirty_ratelimit is low (dirty_ratelimit < balanced_dirty_ratelimit), there is no point to bring up dirty_ratelimit in a hurry only to hurt both the above two goals. So, we make use of task_ratelimit to limit the update of dirty_ratelimit in two ways: 1) avoid changing dirty rate when it's against the position control target (the adjusted rate will slow down the progress of dirty pages going back to setpoint). 2) limit the step size. task_ratelimit is changing values step by step, leaving a consistent trace comparing to the randomly jumping balanced_dirty_ratelimit. task_ratelimit also has the nice smaller errors in stable state and typically larger errors when there are big errors in rate. So it's a pretty good limiting factor for the step size of dirty_ratelimit. Note that bdi->dirty_ratelimit is always tracking balanced_dirty_ratelimit. task_ratelimit is merely used as a limiting factor. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: dirty rate controlWu Fengguang2011-10-032-2/+82
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It's all about bdi->dirty_ratelimit, which aims to be (write_bw / N) when there are N dd tasks. On write() syscall, use bdi->dirty_ratelimit ============================================ balance_dirty_pages(pages_dirtied) { task_ratelimit = bdi->dirty_ratelimit * bdi_position_ratio(); pause = pages_dirtied / task_ratelimit; sleep(pause); } On every 200ms, update bdi->dirty_ratelimit =========================================== bdi_update_dirty_ratelimit() { task_ratelimit = bdi->dirty_ratelimit * bdi_position_ratio(); balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate; bdi->dirty_ratelimit = balanced_dirty_ratelimit } Estimation of balanced bdi->dirty_ratelimit =========================================== balanced task_ratelimit ----------------------- balance_dirty_pages() needs to throttle tasks dirtying pages such that the total amount of dirty pages stays below the specified dirty limit in order to avoid memory deadlocks. Furthermore we desire fairness in that tasks get throttled proportionally to the amount of pages they dirty. IOW we want to throttle tasks such that we match the dirty rate to the writeout bandwidth, this yields a stable amount of dirty pages: dirty_rate == write_bw (1) The fairness requirement gives us: task_ratelimit = balanced_dirty_ratelimit == write_bw / N (2) where N is the number of dd tasks. We don't know N beforehand, but still can estimate balanced_dirty_ratelimit within 200ms. Start by throttling each dd task at rate task_ratelimit = task_ratelimit_0 (3) (any non-zero initial value is OK) After 200ms, we measured dirty_rate = # of pages dirtied by all dd's / 200ms write_bw = # of pages written to the disk / 200ms For the aggressive dd dirtiers, the equality holds dirty_rate == N * task_rate == N * task_ratelimit_0 (4) Or task_ratelimit_0 == dirty_rate / N (5) Now we conclude that the balanced task ratelimit can be estimated by write_bw balanced_dirty_ratelimit = task_ratelimit_0 * ---------- (6) dirty_rate Because with (4) and (5) we can get the desired equality (1): write_bw balanced_dirty_ratelimit == (dirty_rate / N) * ---------- dirty_rate == write_bw / N Then using the balanced task ratelimit we can compute task pause times like: task_pause = task->nr_dirtied / task_ratelimit task_ratelimit with position control ------------------------------------ However, while the above gives us means of matching the dirty rate to the writeout bandwidth, it at best provides us with a stable dirty page count (assuming a static system). In order to control the dirty page count such that it is high enough to provide performance, but does not exceed the specified limit we need another control. The dirty position control works by extending (2) to task_ratelimit = balanced_dirty_ratelimit * pos_ratio (7) where pos_ratio is a negative feedback function that subjects to 1) f(setpoint) = 1.0 2) df/dx < 0 That is, if the dirty pages are ABOVE the setpoint, we throttle each task a bit more HEAVY than balanced_dirty_ratelimit, so that the dirty pages are created less fast than they are cleaned, thus DROP to the setpoints (and the reverse). Based on (7) and the assumption that both dirty_ratelimit and pos_ratio remains CONSTANT for the past 200ms, we get task_ratelimit_0 = balanced_dirty_ratelimit * pos_ratio (8) Putting (8) into (6), we get the formula used in bdi_update_dirty_ratelimit(): write_bw balanced_dirty_ratelimit *= pos_ratio * ---------- (9) dirty_rate Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: add bg_threshold parameter to __bdi_update_bandwidth()Wu Fengguang2011-10-031-4/+7
| | | | | | | | | | | | | | | | | | No behavior change. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: dirty position controlWu Fengguang2011-10-031-1/+190
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | bdi_position_ratio() provides a scale factor to bdi->dirty_ratelimit, so that the resulted task rate limit can drive the dirty pages back to the global/bdi setpoints. Old scheme is, | free run area | throttle area ----------------------------------------+----------------------------> thresh^ dirty pages New scheme is, ^ task rate limit | | * | * | * |[free run] * [smooth throttled] | * | * | * ..bdi->dirty_ratelimit..........* | . * | . * | . * | . * | . * +-------------------------------.-----------------------*------------> setpoint^ limit^ dirty pages The slope of the bdi control line should be 1) large enough to pull the dirty pages to setpoint reasonably fast 2) small enough to avoid big fluctuations in the resulted pos_ratio and hence task ratelimit Since the fluctuation range of the bdi dirty pages is typically observed to be within 1-second worth of data, the bdi control line's slope is selected to be a linear function of bdi write bandwidth, so that it can adapt to slow/fast storage devices well. Assume the bdi control line pos_ratio = 1.0 + k * (dirty - bdi_setpoint) where k is the negative slope. If targeting for 12.5% fluctuation range in pos_ratio when dirty pages are fluctuating in range [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2], we get slope k = - 1 / (8 * write_bw) Let pos_ratio(x_intercept) = 0, we get the parameter used in code: x_intercept = bdi_setpoint + 8 * write_bw The global/bdi slopes are nicely complementing each other when the system has only one major bdi (indicated by bdi_thresh ~= thresh): 1) slope of global control line => scaling to the control scope size 2) slope of main bdi control line => scaling to the writeout bandwidth so that - in memory tight systems, (1) becomes strong enough to squeeze dirty pages inside the control scope - in large memory systems where the "gravity" of (1) for pulling the dirty pages to setpoint is too weak, (2) can back (1) up and drive dirty pages to bdi_setpoint ~= setpoint reasonably fast. Unfortunately in JBOD setups, the fluctuation range of bdi threshold is related to memory size due to the interferences between disks. In this case, the bdi slope will be weighted sum of write_bw and bdi_thresh. Given equations span = x_intercept - bdi_setpoint k = df/dx = - 1 / span and the extremum values span = bdi_thresh dx = bdi_thresh we get df = - dx / span = - 1.0 That means, when bdi_dirty deviates bdi_thresh up, pos_ratio and hence task ratelimit will fluctuate by -100%. peter: use 3rd order polynomial for the global control line CC: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| * | writeback: account per-bdi accumulated dirtied pagesWu Fengguang2011-10-032-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduce the BDI_DIRTIED counter. It will be used for estimating the bdi's dirty bandwidth. CC: Jan Kara <jack@suse.cz> CC: Michael Rubin <mrubin@google.com> CC: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
* | | Merge branch 'for-3.2/core' of git://git.kernel.dk/linux-blockLinus Torvalds2011-11-041-5/+4
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * 'for-3.2/core' of git://git.kernel.dk/linux-block: (29 commits) block: don't call blk_drain_queue() if elevator is not up blk-throttle: use queue_is_locked() instead of lockdep_is_held() blk-throttle: Take blkcg->lock while traversing blkcg->policy_list blk-throttle: Free up policy node associated with deleted rule block: warn if tag is greater than real_max_depth. block: make gendisk hold a reference to its queue blk-flush: move the queue kick into blk-flush: fix invalid BUG_ON in blk_insert_flush block: Remove the control of complete cpu from bio. block: fix a typo in the blk-cgroup.h file block: initialize the bounce pool if high memory may be added later block: fix request_queue lifetime handling by making blk_queue_cleanup() properly shutdown block: drop @tsk from attempt_plug_merge() and explain sync rules block: make get_request[_wait]() fail if queue is dead block: reorganize throtl_get_tg() and blk_throtl_bio() block: reorganize queue draining block: drop unnecessary blk_get/put_queue() in scsi_cmd_ioctl() and blk_get_tg() block: pass around REQ_* flags instead of broken down booleans during request alloc/free block: move blk_throtl prototypes to block/blk.h block: fix genhd refcounting in blkio_policy_parse_and_set() ... Fix up trivial conflicts due to "mddev_t" -> "struct mddev" conversion and making the request functions be of type "void" instead of "int" in - drivers/md/{faulty.c,linear.c,md.c,md.h,multipath.c,raid0.c,raid1.c,raid10.c,raid5.c} - drivers/staging/zram/zram_drv.c
| * | | block: initialize the bounce pool if high memory may be added laterDavid Vrabel2011-10-201-5/+4
| |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | init_emergency_pool() does not create the page pool for bouncing block requests if the current count of high pages is zero. If high memory may be added later (either via memory hotplug or a balloon driver in a virtualized system) then a oops occurs if a request with a high page need bouncing because the pool does not exist. So, always create the pool if memory hotplug is enabled and change the test so it's valid even if all high pages are currently in the balloon (the balloon drivers adjust totalhigh_pages but not max_pfn). Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | | Merge branch 'akpm' (Andrew's incoming - part two)Linus Torvalds2011-11-027-546/+641
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Says Andrew: "60 patches. That's good enough for -rc1 I guess. I have quite a lot of detritus to be rechecked, work through maintainers, etc. - most of the remains of MM - rtc - various misc - cgroups - memcg - cpusets - procfs - ipc - rapidio - sysctl - pps - w1 - drivers/misc - aio" * akpm: (60 commits) memcg: replace ss->id_lock with a rwlock aio: allocate kiocbs in batches drivers/misc/vmw_balloon.c: fix typo in code comment drivers/misc/vmw_balloon.c: determine page allocation flag can_sleep outside loop w1: disable irqs in critical section drivers/w1/w1_int.c: multiple masters used same init_name drivers/power/ds2780_battery.c: fix deadlock upon insertion and removal drivers/power/ds2780_battery.c: add a nolock function to w1 interface drivers/power/ds2780_battery.c: create central point for calling w1 interface w1: ds2760 and ds2780, use ida for id and ida_simple_get() to get it pps gpio client: add missing dependency pps: new client driver using GPIO pps: default echo function include/linux/dma-mapping.h: add dma_zalloc_coherent() sysctl: make CONFIG_SYSCTL_SYSCALL default to n sysctl: add support for poll() RapidIO: documentation update drivers/net/rionet.c: fix ethernet address macros for LE platforms RapidIO: fix potential null deref in rio_setup_device() RapidIO: add mport driver for Tsi721 bridge ...
| * | | mm/page_cgroup.c: quiet sparse noiseH Hartley Sweeten2011-11-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | warning: symbol 'swap_cgroup_ctrl' was not declared. Should it be static? Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: Paul Menage <paul@paulmenage.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Balbir Singh <bsingharora@gmail.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: Fix race condition in memcg_check_events() with this_cpu usageSteven Rostedt2011-11-021-4/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Various code in memcontrol.c () calls this_cpu_read() on the calculations to be done from two different percpu variables, or does an open-coded read-modify-write on a single percpu variable. Disable preemption throughout these operations so that the writes go to the correct palces. [hannes@cmpxchg.org: added this_cpu to __this_cpu conversion] Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Greg Thelen <gthelen@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: close race between charge and putbackJohannes Weiner2011-11-021-1/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There is a potential race between a thread charging a page and another thread putting it back to the LRU list: charge: putback: SetPageCgroupUsed SetPageLRU PageLRU && add to memcg LRU PageCgroupUsed && add to memcg LRU The order of setting one flag and checking the other is crucial, otherwise the charge may observe !PageLRU while the putback observes !PageCgroupUsed and the page is not linked to the memcg LRU at all. Global memory pressure may fix this by trying to isolate and putback the page for reclaim, where that putback would link it to the memcg LRU again. Without that, the memory cgroup is undeletable due to a charge whose physical page can not be found and moved out. Signed-off-by: Johannes Weiner <jweiner@redhat.com> Cc: Ying Han <yinghan@google.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: skip scanning active lists based on individual sizeJohannes Weiner2011-11-022-36/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Reclaim decides to skip scanning an active list when the corresponding inactive list is above a certain size in comparison to leave the assumed working set alone while there are still enough reclaim candidates around. The memcg implementation of comparing those lists instead reports whether the whole memcg is low on the requested type of inactive pages, considering all nodes and zones. This can lead to an oversized active list not being scanned because of the state of the other lists in the memcg, as well as an active list being scanned while its corresponding inactive list has enough pages. Not only is this wrong, it's also a scalability hazard, because the global memory state over all nodes and zones has to be gathered for each memcg and zone scanned. Make these calculations purely based on the size of the two LRU lists that are actually affected by the outcome of the decision. Signed-off-by: Johannes Weiner <jweiner@redhat.com> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <bsingharora@gmail.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: Ying Han <yinghan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: do not expose uninitialized mem_cgroup_per_node to worldIgor Mammedov2011-11-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If somebody is touching data too early, it might be easier to diagnose a problem when dereferencing NULL at mem->info.nodeinfo[node] than trying to understand why mem_cgroup_per_zone is [un|partly]initialized. Signed-off-by: Igor Mammedov <imammedo@redhat.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: fix oom schedule_timeout()KAMEZAWA Hiroyuki2011-11-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Before calling schedule_timeout(), task state should be changed. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | memcg: rename mem variable to memcgRaghavendra K T2011-11-021-463/+467
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The memcg code sometimes uses "struct mem_cgroup *mem" and sometimes uses "struct mem_cgroup *memcg". Rename all mem variables to memcg in source file. Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | cgroup/kmemleak: Annotate alloc_page() for cgroup allocationsSteven Rostedt2011-11-021-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the cgroup base was allocated with kmalloc, it was necessary to annotate the variable with kmemleak_not_leak(). But because it has recently been changed to be allocated with alloc_page() (which skips kmemleak checks) causes a warning on boot up. I was triggering this output: allocated 8388608 bytes of page_cgroup please try 'cgroup_disable=memory' option if you don't want memory cgroups kmemleak: Trying to color unknown object at 0xf5840000 as Grey Pid: 0, comm: swapper Not tainted 3.0.0-test #12 Call Trace: [<c17e34e6>] ? printk+0x1d/0x1f^M [<c10e2941>] paint_ptr+0x4f/0x78 [<c178ab57>] kmemleak_not_leak+0x58/0x7d [<c108ae9f>] ? __rcu_read_unlock+0x9/0x7d [<c1cdb462>] kmemleak_init+0x19d/0x1e9 [<c1cbf771>] start_kernel+0x346/0x3ec [<c1cbf1b4>] ? loglevel+0x18/0x18 [<c1cbf0aa>] i386_start_kernel+0xaa/0xb0 After a bit of debugging I tracked the object 0xf840000 (and others) down to the cgroup code. The change from allocating base with kmalloc to alloc_page() has the base not calling kmemleak_alloc() which adds the pointer to the object_tree_root, but kmemleak_not_leak() adds it to the crt_early_log[] table. On kmemleak_init(), the entry is found in the early_log[] but not the object_tree_root, and this error message is displayed. If alloc_page() fails then it defaults back to vmalloc() which still uses the kmemleak_alloc() which makes us still need the kmemleak_not_leak() call. The solution is to call the kmemleak_alloc() directly if the alloc_page() succeeds. Reviewed-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | mm: thp: tail page refcounting fixAndrea Arcangeli2011-11-024-42/+126
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Michel while working on the working set estimation code, noticed that calling get_page_unless_zero() on a random pfn_to_page(random_pfn) wasn't safe, if the pfn ended up being a tail page of a transparent hugepage under splitting by __split_huge_page_refcount(). He then found the problem could also theoretically materialize with page_cache_get_speculative() during the speculative radix tree lookups that uses get_page_unless_zero() in SMP if the radix tree page is freed and reallocated and get_user_pages is called on it before page_cache_get_speculative has a chance to call get_page_unless_zero(). So the best way to fix the problem is to keep page_tail->_count zero at all times. This will guarantee that get_page_unless_zero() can never succeed on any tail page. page_tail->_mapcount is guaranteed zero and is unused for all tail pages of a compound page, so we can simply account the tail page references there and transfer them to tail_page->_count in __split_huge_page_refcount() (in addition to the head_page->_mapcount). While debugging this s/_count/_mapcount/ change I also noticed get_page is called by direct-io.c on pages returned by get_user_pages. That wasn't entirely safe because the two atomic_inc in get_page weren't atomic. As opposed to other get_user_page users like secondary-MMU page fault to establish the shadow pagetables would never call any superflous get_page after get_user_page returns. It's safer to make get_page universally safe for tail pages and to use get_page_foll() within follow_page (inside get_user_pages()). get_page_foll() is safe to do the refcounting for tail pages without taking any locks because it is run within PT lock protected critical sections (PT lock for pte and page_table_lock for pmd_trans_huge). The standard get_page() as invoked by direct-io instead will now take the compound_lock but still only for tail pages. The direct-io paths are usually I/O bound and the compound_lock is per THP so very finegrined, so there's no risk of scalability issues with it. A simple direct-io benchmarks with all lockdep prove locking and spinlock debugging infrastructure enabled shows identical performance and no overhead. So it's worth it. Ideally direct-io should stop calling get_page() on pages returned by get_user_pages(). The spinlock in get_page() is already optimized away for no-THP builds but doing get_page() on tail pages returned by GUP is generally a rare operation and usually only run in I/O paths. This new refcounting on page_tail->_mapcount in addition to avoiding new RCU critical sections will also allow the working set estimation code to work without any further complexity associated to the tail page refcounting with THP. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Michel Lespinasse <walken@google.com> Reviewed-by: Michel Lespinasse <walken@google.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: <stable@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | | filesystems: add missing nlink wrappersMiklos Szeredi2011-11-021-1/+1
|/ / / | | | | | | | | | | | | | | | | | | Replace direct i_nlink updates with the respective updater function (inc_nlink, drop_nlink, clear_nlink, inode_dec_link_count). Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
* | | mm/vmstat.c: cache align vm_statDimitri Sivanich2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Avoid false sharing of the vm_stat array. This was found to adversely affect tmpfs I/O performance. Tests run on a 640 cpu UV system. With 120 threads doing parallel writes, each to different tmpfs mounts: No patch: ~300 MB/sec With vm_stat alignment: ~430 MB/sec Signed-off-by: Dimitri Sivanich <sivanich@sgi.com> Acked-by: Christoph Lameter <cl@gentwo.org> Acked-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: munlock use mapcount to avoid terrible overheadHugh Dickins2011-10-311-1/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A process spent 30 minutes exiting, just munlocking the pages of a large anonymous area that had been alternately mprotected into page-sized vmas: for every single page there's an anon_vma walk through all the other little vmas to find the right one. A general fix to that would be a lot more complicated (use prio_tree on anon_vma?), but there's one very simple thing we can do to speed up the common case: if a page to be munlocked is mapped only once, then it is our vma that it is mapped into, and there's no need whatever to walk through all the others. Okay, there is a very remote race in munlock_vma_pages_range(), if between its follow_page() and lock_page(), another process were to munlock the same page, then page reclaim remove it from our vma, then another process mlock it again. We would find it with page_mapcount 1, yet it's still mlocked in another process. But never mind, that's much less likely than the down_read_trylock() failure which munlocking already tolerates (in try_to_unmap_one()): in due course page reclaim will discover and move the page to unevictable instead. [akpm@linux-foundation.org: add comment] Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Michel Lespinasse <walken@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/huge_memory: fix typo when updating mmu cacheHillf Danton2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are three cases of update_mmu_cache() in the file, and the case in function collapse_huge_page() has a typo, namely the last parameter used, which is corrected based on the other two cases. Due to the define of update_mmu_cache by X86, the only arch that implements THP currently, the change here has no really crystal point, but one or two minutes of efforts could be saved for those archs that are likely to support THP in future. Signed-off-by: Hillf Danton <dhillf@gmail.com> Cc: Johannes Weiner <jweiner@redhat.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/huge_memory: fix copying user highpageHillf Danton2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The THP copy-on-write handler falls back to regular-sized pages for a huge page replacement upon allocation failure or if THP has been individually disabled in the target VMA. The loop responsible for copying page-sized chunks accidentally uses multiples of PAGE_SHIFT instead of PAGE_SIZE as the virtual address arg for copy_user_highpage(). Signed-off-by: Hillf Danton <dhillf@gmail.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: do not drain pagevecs for mlockall(MCL_FUTURE)Christoph Lameter2011-10-311-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | MCL_FUTURE does not move pages between lru list and draining the LRU per cpu pagevecs is a nasty activity. Avoid doing it unecessarily. Signed-off-by: Christoph Lameter <cl@gentwo.org> Cc: David Rientjes <rientjes@google.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Acked-by: Johannes Weiner <jweiner@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | vmscan: abort reclaim/compaction if compaction can proceedMel Gorman2011-10-311-11/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If compaction can proceed, shrink_zones() stops doing any work but its callers still call shrink_slab() which raises the priority and potentially sleeps. This is unnecessary and wasteful so this patch aborts direct reclaim/compaction entirely if compaction can proceed. Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Cc: Josh Boyer <jwboyer@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | vmscan: limit direct reclaim for higher order allocationsRik van Riel2011-10-311-0/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When suffering from memory fragmentation due to unfreeable pages, THP page faults will repeatedly try to compact memory. Due to the unfreeable pages, compaction fails. Needless to say, at that point page reclaim also fails to create free contiguous 2MB areas. However, that doesn't stop the current code from trying, over and over again, and freeing a minimum of 4MB (2UL << sc->order pages) at every single invocation. This resulted in my 12GB system having 2-3GB free memory, a corresponding amount of used swap and very sluggish response times. This can be avoided by having the direct reclaim code not reclaim from zones that already have plenty of free memory available for compaction. If compaction still fails due to unmovable memory, doing additional reclaim will only hurt the system, not help. [jweiner@redhat.com: change comment to explain the order check] Signed-off-by: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Johannes Weiner <jweiner@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | vmscan: add barrier to prevent evictable page in unevictable listMinchan Kim2011-10-312-5/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a race between putback_lru_page() and shmem_lock with lock=0 happens, progrom execution order is as follows, but clear_bit in processor #1 could be reordered right before spin_unlock of processor #1. Then, the page would be stranded on the unevictable list. spin_lock SetPageLRU spin_unlock clear_bit(AS_UNEVICTABLE) spin_lock if PageLRU() if !test_bit(AS_UNEVICTABLE) move evictable list smp_mb if !test_bit(AS_UNEVICTABLE) move evictable list spin_unlock But, pagevec_lookup() in scan_mapping_unevictable_pages() has rcu_read_[un]lock() so it could protect reordering before reaching test_bit(AS_UNEVICTABLE) on processor #1 so this problem never happens. But it's a unexpected side effect and we should solve this problem properly. This patch adds a barrier after mapping_clear_unevictable. I didn't meet this problem but just found during review. Signed-off-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik van Riel <riel@redhat.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/huge_memory.c: quiet sparse noiseH Hartley Sweeten2011-10-311-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quiet the sparse noise: warning: symbol 'khugepaged_scan' was not declared. Should it be static? warning: context imbalance in 'khugepaged_scan_mm_slot' - unexpected unlock Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/mempolicy.c: quiet sparse noiseH Hartley Sweeten2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quiet the spares noise: warning: symbol 'default_policy' was not declared. Should it be static? Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Stephen Wilson <wilsons@start.ca> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/thrash.c: quiet sparse noiseH Hartley Sweeten2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quiet the following sparse noise: warning: symbol 'swap_token_memcg' was not declared. Should it be static? Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: Rik van Riel <riel@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm/memblock.c: quiet sparse noiseH Hartley Sweeten2011-10-311-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Quiet the following sparse noise in this file: warning: symbol 'memblock_overlaps_region' was not declared. Should it be static? Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers,com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: "H. Peter Anvin" <hpa@linux.intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Tomi Valkeinen <tomi.valkeinen@nokia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: disable user interface to manually rescue unevictable pagesJohannes Weiner2011-10-311-76/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | At one point, anonymous pages were supposed to go on the unevictable list when no swap space was configured, and the idea was to manually rescue those pages after adding swap and making them evictable again. But nowadays, swap-backed pages on the anon LRU list are not scanned without available swap space anyway, so there is no point in moving them to a separate list anymore. The manual rescue could also be used in case pages were stranded on the unevictable list due to race conditions. But the code has been around for a while now and newly discovered bugs should be properly reported and dealt with instead of relying on such a manual fixup. In addition to the lack of a usecase, the sysfs interface to rescue pages from a specific NUMA node has been broken since its introduction, so it's unlikely that anybody ever relied on that. This patch removes the functionality behind the sysctl and the node-interface and emits a one-time warning when somebody tries to access either of them. Signed-off-by: Johannes Weiner <jweiner@redhat.com> Reported-by: Kautuk Consul <consul.kautuk@gmail.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | vmscan.c: fix invalid strict_strtoul() check in write_scan_unevictable_node()Kautuk Consul2011-10-311-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | write_scan_unevictable_node() checks the value req returned by strict_strtoul() and returns 1 if req is 0. However, when strict_strtoul() returns 0, it means successful conversion of buf to unsigned long. Due to this, the function was not proceeding to scan the zones for unevictable pages even though we write a valid value to the scan_unevictable_pages sys file. Change this check slightly to check for invalid value in buf as well as 0 value stored in res after successful conversion via strict_strtoul. In both cases, we do not perform the scanning of this node's zones. Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: fix kunmap_high() commentLi Haifeng2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | Signed-off-by: Li Haifeng <omycle@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | mm: compaction: make compact_zone_order() staticKyungmin Park2011-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's no compact_zone_order() user outside file scope, so make it static. Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Acked-by: David Rientjes <rientjes@google.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>