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* Prevent going idle with softirq pendingThomas Gleixner2007-05-231-3/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The NOHZ patch contains a check for softirqs pending when a CPU goes idle. The BUG is unrelated to NOHZ, it just was made visible by the NOHZ patch. The BUG showed up mainly on P4 / hyperthreading enabled machines which lead the investigations into the wrong direction in the first place. The real cause is in cond_resched_softirq(): cond_resched_softirq() is enabling softirqs without invoking the softirq daemon when softirqs are pending. This leads to the warning message in the NOHZ idle code: t1 runs softirq disabled code on CPU#0 interrupt happens, softirq is raised, but deferred (softirqs disabled) t1 calls cond_resched_softirq() enables softirqs via _local_bh_enable() calls schedule() t2 runs t1 is migrated to CPU#1 t2 is done and invokes idle() NOHZ detects the pending softirq Fix: change _local_bh_enable() to local_bh_enable() so the softirq daemon is invoked. Thanks to Anant Nitya for debugging this with great patience ! Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Add suspend-related notifications for CPU hotplugRafael J. Wysocki2007-05-091-0/+10
| | | | | | | | | | | | | | | | | | | | | Since nonboot CPUs are now disabled after tasks and devices have been frozen and the CPU hotplug infrastructure is used for this purpose, we need special CPU hotplug notifications that will help the CPU-hotplug-aware subsystems distinguish normal CPU hotplug events from CPU hotplug events related to a system-wide suspend or resume operation in progress. This patch introduces such notifications and causes them to be used during suspend and resume transitions. It also changes all of the CPU-hotplug-aware subsystems to take these notifications into consideration (for now they are handled in the same way as the corresponding "normal" ones). [oleg@tv-sign.ru: cleanups] Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Pavel Machek <pavel@ucw.cz> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Eliminate lock_cpu_hotplug in kernel/schedcGautham R Shenoy2007-05-091-10/+18
| | | | | | | | | | | | | | Eliminate lock_cpu_hotplug from kernel/sched.c and use sched_hotcpu_mutex instead to postpone a hotplug event. In the migration_call hotcpu callback function, take sched_hotcpu_mutex while handling the event CPU_LOCK_ACQUIRE and release it while handling CPU_LOCK_RELEASE event. [akpm@linux-foundation.org: fix deadlock] Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* revert 'sched: redundant reschedule when set_user_nice() boosts a prio of a ↵Andrew Morton2007-05-081-16/+18
| | | | | | | | | | | | | | | | | | | | | | | | | task from the "expired" array' Revert commit bd53f96ca54a21c07e7a0ae1886fa623d370b85f. Con says: This is no good, sorry. The one I saw originally was with the staircase deadline cpu scheduler in situ and was different. #define TASK_PREEMPTS_CURR(p, rq) \ ((p)->prio < (rq)->curr->prio) (((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active)) This will fail to wake up a runqueue for a task that has been migrated to the expired array of a runqueue which is otherwise idle which can happen with smp balancing, Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com> Cc: Con Kolivas <kernel@kolivas.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: align rq to cacheline boundarySiddha, Suresh B2007-05-081-1/+1
| | | | | | | | | | | | Align the per cpu runqueue to the cacheline boundary. This will minimize the number of cachelines touched during remote wakeup. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Ravikiran G Thirumalai <kiran@scalex86.org> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: redundant reschedule when set_user_nice() boosts a prio of a task ↵Dmitry Adamushko2007-05-081-18/+16
| | | | | | | | | | | | | | | | | | | from the "expired" array - Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's prio is higher than the current's one and the task is in the "active" array. This ensures we don't make redundant resched_task() calls when the task is in the "expired" array (as may happen now in set_user_prio(), rt_mutex_setprio() and pull_task() ) ; - generalise conditions for a call to resched_task() in set_user_nice(), rt_mutex_setprio() and sched_setscheduler() Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> Cc: Con Kolivas <kernel@kolivas.org> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: optimize siblings status check logic in wake_idle()Siddha, Suresh B2007-05-081-1/+10
| | | | | | | | | | | | | | | | When a logical cpu 'x' already has more than one process running, then most likely the siblings of that cpu 'x' must be busy. Otherwise the idle siblings would have likely(in most of the scenarios) picked up the extra load making the load on 'x' atmost one. Use this logic to eliminate the siblings status check and minimize the cache misses encountered on a heavily loaded system. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Speed up divides by cpu_power in schedulerEric Dumazet2007-05-081-29/+54
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I noticed expensive divides done in try_to_wakeup() and find_busiest_group() on a bi dual core Opteron machine (total of 4 cores), moderatly loaded (15.000 context switch per second) oprofile numbers : CPU: AMD64 processors, speed 2600.05 MHz (estimated) Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit mask of 0x00 (No unit mask) count 50000 samples % symbol name ... 613914 1.0498 try_to_wake_up 834 0.0013 :ffffffff80227ae1: div %rcx 77513 0.1191 :ffffffff80227ae4: mov %rax,%r11 608893 1.0413 find_busiest_group 1841 0.0031 :ffffffff802260bf: div %rdi 140109 0.2394 :ffffffff802260c2: test %sil,%sil Some of these divides can use the reciprocal divides we introduced some time ago (currently used in slab AFAIK) We can assume a load will fit in a 32bits number, because with a SCHED_LOAD_SCALE=128 value, its still a theorical limit of 33554432 When/if we reach this limit one day, probably cpus will have a fast hardware divide and we can zap the reciprocal divide trick. Ingo suggested to rename cpu_power to __cpu_power to make clear it should not be modified without changing its reciprocal value too. I did not convert the divide in cpu_avg_load_per_task(), because tracking nr_running changes may be not worth it ? We could use a static table of 32 reciprocal values but it would add a conditional branch and table lookup. [akpm@linux-foundation.org: !SMP build fix] Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: dynticks idle load balancingSiddha, Suresh B2007-05-081-13/+210
| | | | | | | | | | | | | | | | | | | | | | | | Fix the process idle load balancing in the presence of dynticks. cpus for which ticks are stopped will sleep till the next event wakes it up. Potentially these sleeps can be for large durations and during which today, there is no periodic idle load balancing being done. This patch nominates an owner among the idle cpus, which does the idle load balancing on behalf of the other idle cpus. And once all the cpus are completely idle, then we can stop this idle load balancing too. Checks added in fast path are minimized. Whenever there are busy cpus in the system, there will be an owner(idle cpu) doing the system wide idle load balancing. Open items: 1. Intelligent owner selection (like an idle core in a busy package). 2. Merge with rcu's nohz_cpu_mask? Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: fix idle load balancing in softirqd contextSiddha, Suresh B2007-05-081-7/+5
| | | | | | | | | | | | | | | | | | Periodic load balancing in recent kernels happen in the softirq. In certain -rt configurations, these softirqs are handled in softirqd context. And hence the check for idle processor was always returning busy (as nr_running > 1). This patch captures the idle information at the tick and passes this info to softirq context through an element 'idle_at_tick' in rq. [kernel@kolivas.org: Fix reverse idle at tick logic] Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* add touch_all_softlockup_watchdogs()Jeremy Fitzhardinge2007-05-081-0/+2
| | | | | | | | | | | | | | | | | | | | Add touch_all_softlockup_watchdogs() to allow the softlockup watchdog timers on all cpus to be updated. This is used to prevent sysrq-t from generating a spurious watchdog message when generating lots of output. Softlockup watchdogs use sched_clock() as its timebase, which is inherently per-cpu (at least, when it is measuring unstolen time). Because of this, it isn't possible for one CPU to directly update the other CPU's timers, but it is possible to tell the other CPUs to do update themselves appropriately. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Acked-by: Chris Lalancette <clalance@redhat.com> Signed-off-by: Prarit Bhargava <prarit@redhat.com> Cc: Rick Lindsley <ricklind@us.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Safer nr_node_ids and nr_node_ids determination and initial valuesChristoph Lameter2007-05-071-0/+8
| | | | | | | | | | | | | | | | | | The nr_cpu_ids value is currently only calculated in smp_init. However, it may be needed before (SLUB needs it on kmem_cache_init!) and other kernel components may also want to allocate dynamically sized per cpu array before smp_init. So move the determination of possible cpus into sched_init() where we already loop over all possible cpus early in boot. Also initialize both nr_node_ids and nr_cpu_ids with the highest value they could take. If we have accidental users before these values are determined then the current valud of 0 may cause too small per cpu and per node arrays to be allocated. If it is set to the maximum possible then we only waste some memory for early boot users. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* make SysRq-T show all tasks againIngo Molnar2007-04-271-1/+1
| | | | | | | | | | | | | | | show_state() (SysRq-T) developed the buggy habbit of not showing TASK_RUNNING tasks. This was due to the mistaken belief that state_filter == -1 would be a pass-through filter - while in reality it did not let TASK_RUNNING == 0 p->state values through. Fix this by restoring the original '!state_filter means all tasks' special-case i had in the original version. Test-built and test-booted on i686, SysRq-T now works as intended. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched.c: Remove unused variable 'relative'Linus Torvalds2007-04-071-1/+0
| | | | | | | Getting rid of the p->children printout in show_task() left behind an unused variable. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] sched: get rid of p->children use in show_task()Ingo Molnar2007-04-071-34/+1
| | | | | | | | | | | | | | | | | | | | | | | | the p->parent PID printout gives us all the information about the task tree that we need - the eldest_child()/older_sibling()/ younger_sibling() printouts are mostly historic and i do not remember ever having used those fields. (IMO in fact they confuse the SysRq-T output.) So remove them. This code has sentimental value though, those fields and printouts are one of the oldest ones still surviving from Linux v0.95's kernel/sched.c: if (p->p_ysptr || p->p_osptr) printk(" Younger sib=%d, older sib=%d\n\r", p->p_ysptr ? p->p_ysptr->pid : -1, p->p_osptr ? p->p_osptr->pid : -1); else printk("\n\r"); written 15 years ago, in early 1992. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus 'snif' Torvalds <torvalds@linux-foundation.org>
* [PATCH] sched: remove SMT niceCon Kolivas2007-03-051-154/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | Remove the SMT-nice feature which idles sibling cpus on SMT cpus to facilitiate nice working properly where cpu power is shared. The idling of cpus in the presence of runnable tasks is considered too fragile, easy to break with outside code, and the complexity of managing this system if an architecture comes along with many logical cores sharing cpu power will be unworkable. Remove the associated per_cpu_gain variable in sched_domains used only by this code. Also: The reason is that with dynticks enabled, this code breaks without yet further tweaks so dynticks brought on the rapid demise of this code. So either we tweak this code or kill it off entirely. It was Ingo's preference to kill it off. Either way this needs to happen for 2.6.21 since dynticks has gone in. Signed-off-by: Con Kolivas <kernel@kolivas.org> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] sched: fix SMT scheduler bugIngo Molnar2007-03-011-1/+1
| | | | | | | | | | | | | | | | | | | | The SMT scheduler incorrectly skips kernel threads even if they are runnable (but they are preempted by a higher-prio user-space task which got SMT-delayed by an even higher-priority task running on a sibling CPU). Fix this for now by only doing the SMT-nice optimization if the to-be-delayed task is the only runnable task. (This should cover most of the real-life cases anyway.) This bug has been in the SMT scheduler since 2.6.17 or so, but has only been noticed now by the active check in the dynticks code. Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran valueThomas Gleixner2007-03-011-1/+1
| | | | | | | | | | | | | | | | | | | | Problem description at: http://bugzilla.kernel.org/show_bug.cgi?id=8048 Commit b18ec80396834497933d77b81ec0918519f4e2a7 [PATCH] sched: improve migration accuracy optimized the scheduler time calculations, but broke posix-cpu-timers. The problem is that the p->last_ran value is not updated after a context switch. So a subsequent call to current_sched_time() calculates with a stale p->last_ran value, i.e. accounts the full time, which the task was scheduled away. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] i386: paravirt CPU hypercall batching modeZachary Amsden2007-02-131-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | The VMI ROM has a mode where hypercalls can be queued and batched. This turns out to be a significant win during context switch, but must be done at a specific point before side effects to CPU state are visible to subsequent instructions. This is similar to the MMU batching hooks already provided. The same hooks could be used by the Xen backend to implement a context switch multicall. To explain a bit more about lazy modes in the paravirt patches, basically, the idea is that only one of lazy CPU or MMU mode can be active at any given time. Lazy MMU mode is similar to this lazy CPU mode, and allows for batching of multiple PTE updates (say, inside a remap loop), but to avoid keeping some kind of state machine about when to flush cpu or mmu updates, we just allow one or the other to be active. Although there is no real reason a more comprehensive scheme could not be implemented, there is also no demonstrated need for this extra complexity. Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Andi Kleen <ak@suse.de> Cc: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
* [PATCH] sched: avoid div in rebalance_tickNick Piggin2007-02-121-3/+5
| | | | | | | | | | | | | | | | Avoid expensive integer divide 3 times per CPU per tick. A userspace test of this loop went from 26ns, down to 19ns on a G5; and from 123ns down to 28ns on a P3. (Also avoid a variable bit shift, as suggested by Alan. The effect of this wasn't noticable on the CPUs I tested with). Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] Numerous fixes to kernel-doc info in source files.Robert P. J. Day2007-02-111-5/+4
| | | | | | | | | | | | | | | A variety of (mostly) innocuous fixes to the embedded kernel-doc content in source files, including: * make multi-line initial descriptions single line * denote some function names, constants and structs as such * change erroneous opening '/*' to '/**' in a few places * reword some text for clarity Signed-off-by: Robert P. J. Day <rpjday@mindspring.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] Consolidate default sched_clock()Alexey Dobriyan2007-02-111-0/+10
| | | | | | | | | Use attribute(weak). Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] sched: tasks cannot run on cpus onlined after bootNathan Lynch2007-01-111-1/+1
| | | | | | | | | | | | | | | | | | | | | Commit 5c1e176781f43bc902a51e5832f789756bff911b ("sched: force /sbin/init off isolated cpus") sets init's cpus_allowed to a subset of cpu_online_map at boot time, which means that tasks won't be scheduled on cpus that are added to the system later. Make init's cpus_allowed a subset of cpu_possible_map instead. This should still preserve the behavior that Nick's change intended. Thanks to Giuliano Pochini for reporting this and testing the fix: http://ozlabs.org/pipermail/linuxppc-dev/2006-December/029397.html Signed-off-by: Nathan Lynch <ntl@pobox.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: fix cond_resched_softirq() offsetIngo Molnar2006-12-301-14/+4
| | | | | | | | | | | | | | | | | | | | | | | | | Remove the __resched_legal() check: it is conceptually broken. The biggest problem it had is that it can mask buggy cond_resched() calls. A cond_resched() call is only legal if we are not in an atomic context, with two narrow exceptions: - if the system is booting - a reacquire_kernel_lock() down() done while PREEMPT_ACTIVE is set But __resched_legal() hid this and just silently returned whenever these primitives were called from invalid contexts. (Same goes for cond_resched_locked() and cond_resched_softirq()). Furthermore, the __legal_resched(0) call was buggy in that it caused unnecessarily long softirq latencies via cond_resched_softirq(). (which is only called from softirq-off sections, hence the code did nothing.) The fix is to resurrect the efficiency of the might_sleep checks and to only allow the narrow exceptions. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: remove __cpuinitdata anotation to cpu_isolated_mapTim Chen2006-12-221-1/+1
| | | | | | | | | | | | | | The structure cpu_isolated_map is used not only during initialization. Multi-core scheduler configuration changes and exclusive cpusets use this during run time. During setting of sched_mc_power_savings policy, this structure is accessed to update sched_domains. Signed-off-by: Tim Chen <tim.c.chen@intel.com> Acked-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Conditionally check expected_preempt_count in __resched_legal()Mark Fasheh2006-12-221-0/+2
| | | | | | | | | | | | | | | | | | | | | | Commit 2d7d253548cffdce80f4e03664686e9ccb1b0ed7 ("fix cond_resched() fix") introduced an 'expected_preempt_count' parameter to __resched_legal() to fix a bug where it was returning a false negative when called from cond_resched_lock() and preemption was enabled. Unfortunately this broke things for when preemption is disabled. preempt_count() will always return zero, thus failing the check against any value of expected_preempt_count not equal to zero. cond_resched_lock() for example, passes an expected_preempt_count value of 1. So fix the fix for the cond_resched() fix by skipping the check of preempt_count() against expected_preempt_count when preemption is disabled. Credit should go to Sunil Mushran for spotting the bug during testing. Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: improve efficiency of sched_fork()Peter Williams2006-12-211-1/+2
| | | | | | | | | | | | | | | | | | | | | | Problem: sched_fork() has always called scheduler_tick() in some (unlikely) circumstances in order to update the current task in light of those circumstances. It has always been the case that the work done by scheduler_tick() was more than was required to handle the problem in hand but no harm was done except for the waste of a few CPU cycles. However, the splitting of scheduler_tick() into two procedures in 2.6.20-rc1 enables the wasted cycles to be saved as the new procedure task_running_tick() does all the work that is required to rectify the problem being handled. Solution: Replace the call to scheduler_tick() in sched_fork() with a call to task_running_tick(). Signed-off-by: Peter Williams <pwil3058@bigpond.com.au> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] lockdep: print irq-trace info on assertsIngo Molnar2006-12-131-0/+4
| | | | | | | | | | | | When we print an assert due to scheduling-in-atomic bugs, and if lockdep is enabled, then the IRQ tracing information of lockdep can be printed to pinpoint the code location that disabled interrupts. This saved me quite a bit of debugging time in cases where the backtrace did not identify the irq-disabling site well enough. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kernel/sched.c: whitespace cleanupsMiguel Ojeda Sandonis2006-12-101-40/+55
| | | | | | | | | [akpm@osdl.org: additional cleanups] Signed-off-by: Miguel Ojeda Sandonis <maxextreme@gmail.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: optimize activate_task for RT taskChen, Kenneth W2006-12-101-3/+5
| | | | | | | | | | | | | | RT task does not participate in interactiveness priority and thus shouldn't be bothered with timestamp and p->sleep_type manipulation when task is being put on run queue. Bypass all of the them with a single if (rt_task) test. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: remove lb_stopbalance counterChen, Kenneth W2006-12-101-7/+4
| | | | | | | | | | | | Remove scheduler stats lb_stopbalance counter. This counter can be calculated by: lb_balanced - lb_nobusyg - lb_nobusyq. There is no need to create gazillion counters while we can derive the value. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: decrease number of load balancesSiddha, Suresh B2006-12-101-12/+47
| | | | | | | | | | | | | | | | | | | | Currently at a particular domain, each cpu in the sched group will do a load balance at the frequency of balance_interval. More the cores and threads, more the cpus will be in each sched group at SMP and NUMA domain. And we endup spending quite a bit of time doing load balancing in those domains. Fix this by making only one cpu(first idle cpu or first cpu in the group if all the cpus are busy) in the sched group do the load balance at that particular sched domain and this load will slowly percolate down to the other cpus with in that group(when they do load balancing at lower domains). Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Christoph Lameter <clameter@engr.sgi.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: improve migration accuracyMike Galbraith2006-12-101-21/+20
| | | | | | | | | | | | | | | | | | | | | Co-opt rq->timestamp_last_tick to maintain a cache_hot_time evaluation reference timestamp at both tick and sched times to prevent said reference, formerly rq->timestamp_last_tick, from being behind task->last_ran at evaluation time, and to move said reference closer to current time on the remote processor, intent being to improve cache hot evaluation and timestamp adjustment accuracy for task migration. Fix minor sched_time double accounting error which occurs when a task passing through schedule() does not schedule off, and takes the next timer tick. [kenneth.w.chen@intel.com: cleanup] Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Ken Chen <kenneth.w.chen@intel.com> Cc: Don Mullis <dwm@meer.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: add option to serialize load balancingChristoph Lameter2006-12-101-0/+9
| | | | | | | | | | | | | | | | | | Large sched domains can be very expensive to scan. Add an option SD_SERIALIZE to the sched domain flags. If that flag is set then we make sure that no other such domain is being balanced. [akpm@osdl.org: build fix] Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: call tasklet less frequentlyChristoph Lameter2006-12-101-2/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Trigger softirq less frequently We trigger the softirq before this patch using offset of sd->interval. However, if the queue is busy then it is sufficient to schedule the softirq with sd->interval * busy_factor. So we modify the calculation of the next time to balance by taking the interval added to last_balance again. This is only the right value if the idle/busy situation continues as is. There are two potential trouble spots: - If the queue was idle and now gets busy then we call rebalance early. However, that is not a problem because we will then use the longer interval for the next period. - If the queue was busy and becomes idle then we potentially wait too long before rebalancing. However, when the task goes idle then idle_balance is called. We add another calculation of the next balance time based on sd->interval in idle_balance so that we will rebalance soon. V2->V3: - Calculate rebalance time based on current jiffies and not based on the jiffies at the last time we load balanced. We no longer rely on staggering and therefore we can affort to do this now. V3->V4: - Use functions to do jiffy comparisons. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: use softirq for load balancingChristoph Lameter2006-12-101-5/+17
| | | | | | | | | | | | | | | | | | | | Call rebalance_tick (renamed to run_rebalance_domains) from a newly introduced softirq. We calculate the earliest time for each layer of sched domains to be rescanned (this is the rescan time for idle) and use the earliest of those to schedule the softirq via a new field "next_balance" added to struct rq. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: move idle status calculation into rebalance_tick()Christoph Lameter2006-12-101-21/+16
| | | | | | | | | | | | | | | | | | | | | | Perform the idle state determination in rebalance_tick. If we separate balancing from sched_tick then we also need to determine the idle state in rebalance_tick. V2->V3 Remove useless idlle != 0 check. Checking nr_running seems to be sufficient. Thanks Suresh. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: extract load calculation from rebalance_tickChristoph Lameter2006-12-101-42/+54
| | | | | | | | | | | | | | | | | | | | | | A load calculation is always done in rebalance_tick() in addition to the real load balancing activities that only take place when certain jiffie counts have been reached. Move that processing into a separate function and call it directly from scheduler_tick(). Also extract the time slice handling from scheduler_tick and put it into a separate function. Then we can clean up scheduler_tick significantly. It will no longer have any gotos. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: disable interrupts for locking in load_balance()Christoph Lameter2006-12-101-5/+6
| | | | | | | | | | | | | | | | Interrupts must be disabled for request queue locks if we want to run load_balance() with interrupts enabled. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: remove staggering of load balancingChristoph Lameter2006-12-101-8/+2
| | | | | | | | | | | | | | | | | | | | | Timer interrupts already are staggered. We do not need an additional layer of time staggering for short load balancing actions that take a reasonably small portion of the time slice. For load balancing on large sched_domains we will add a serialization later that avoids concurrent load balance operations and thus has the same effect as load staggering. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: avoid taking rq lock in wake_priority_sleeperChristoph Lameter2006-12-101-0/+3
| | | | | | | | | | | | | | | | Avoid taking the request queue lock in wake_priority_sleeper if there are no running processes. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Peter Williams <pwil3058@bigpond.net.au> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Christoph Lameter <clameter@sgi.com> Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] move_task_off_dead_cpu() should be called with disabled intsKirill Korotaev2006-12-101-3/+14
| | | | | | | | | | | | | move_task_off_dead_cpu() requires interrupts to be disabled, while migrate_dead() calls it with enabled interrupts. Added appropriate comments to functions and added BUG_ON(!irqs_disabled()) into double_rq_lock() and double_lock_balance() which are the origin sources of such bugs. Signed-off-by: Kirill Korotaev <dev@openvz.org> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] ched domain: move sched group allocations to percpu areaSiddha, Suresh B2006-12-101-68/+64
| | | | | | | | | | | | Move the sched group allocations to percpu area. This will minimize cross node memory references and also cleans up the sched groups allocation for allnodes sched domain. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched.c: correct comment for this_rq_lock()Robert P. J. Day2006-12-101-1/+1
| | | | | | | Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Robert P. J. Day <rpjday@mindspring.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] struct seq_operations and struct file_operations constificationHelge Deller2006-12-071-1/+1
| | | | | | | | | | | | | | - move some file_operations structs into the .rodata section - move static strings from policy_types[] array into the .rodata section - fix generic seq_operations usages, so that those structs may be defined as "const" as well [akpm@osdl.org: couple of fixes] Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sched: correct output of show_state()Chris Caputo2006-12-071-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | At present show_state prints a header the does not match the output of show_task, as follows: - sibling task PC pid father child younger older init S 00000000 0 1 0 2 (NOTLB) - This patch corrects the output of show_state so that the header is aligned with the data, ala: - free sibling task PC stack pid father child younger older init S 00000000 0 1 0 2 (NOTLB) - Signed-off-by: Chris Caputo <ccaputo@alt.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] hotplug CPU: clean up hotcpu_notifier() useIngo Molnar2006-12-071-3/+0
| | | | | | | | | | | | | | | | | | There was lots of #ifdef noise in the kernel due to hotcpu_notifier(fn, prio) not correctly marking 'fn' as used in the !HOTPLUG_CPU case, and thus generating compiler warnings of unused symbols, hence forcing people to add #ifdefs. the compiler can skip truly unused functions just fine: text data bss dec hex filename 1624412 728710 3674856 6027978 5bfaca vmlinux.before 1624412 728710 3674856 6027978 5bfaca vmlinux.after [akpm@osdl.org: topology.c fix] Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sleep profilingIngo Molnar2006-12-071-0/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement prof=sleep profiling. TASK_UNINTERRUPTIBLE sleeps will be taken as a profile hit, and every millisecond spent sleeping causes a profile-hit for the call site that initiated the sleep. Sample readprofile output on i386: 306 ps2_sendbyte 1.3973 432 call_usermodehelper_keys 1.9548 484 ps2_command 0.6453 790 __driver_attach 4.7879 1593 msleep 44.2500 3976 sync_buffer 64.1290 4076 do_lookup 12.4648 8587 sync_page 122.6714 20820 total 0.0067 (NOTE: architectures need to check whether get_wchan() can be called from deep within the wakeup path.) akpm: we need to mark more functions __sched. lock_sock(), msleep(), others.. akpm: the contention in do_lookup() is a surprise. Presumably doing disk reads for directory contents while holding i_mutex. [akpm@osdl.org: various fixes] Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] lockdep: print current locks on in_atomic warningsPeter Zijlstra2006-12-071-0/+2
| | | | | | | | | | Add debug_show_held_locks(current) to __might_sleep() and schedule(); this makes finding the offending lock leak easier. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] SysRq-X: show blocked tasksIngo Molnar2006-12-071-3/+8
| | | | | | | | | | Add SysRq-X support: show blocked (TASK_UNINTERRUPTIBLE) tasks only. Useful for debugging IO stalls. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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