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* blk-throttle: cap discard request sizeShaohua Li2017-08-231-4/+14
| | | | | | | | | | | | discard request usually is very big and easily use all bandwidth budget of a cgroup. discard request size doesn't really mean the size of data written, so it doesn't make sense to account it into bandwidth budget. Jens pointed out treating the size 0 doesn't make sense too, because discard request does have cost. But it's not easy to find the actual cost. This patch simply makes the size one sector. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-throttle: set default latency baseline for harddiskShaohua Li2017-06-071-3/+17
| | | | | | | | | | | | | | | | | | hard disk IO latency varies a lot depending on spindle move. The latency range could be from several microseconds to several milliseconds. It's pretty hard to get the baseline latency used by io.low. We will use a different stragety here. The idea is only using IO with spindle move to determine if cgroup IO is in good state. For HD, if io latency is small (< 1ms), we ignore the IO. Such IO is likely from sequential IO, and is helpless to help determine if a cgroup's IO is impacted by other cgroups. With this, we only account IO with big latency. Then we can choose a hardcoded baseline latency for HD (4ms, which is typical IO latency with seek). With all these settings, the io.low latency works for both HD and SSD. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: fix NULL pointer dereference in throtl_schedule_pending_timerJoseph Qi2017-06-071-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | I have encountered a NULL pointer dereference in throtl_schedule_pending_timer: [ 413.735396] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 [ 413.735535] IP: [<ffffffff812ebbbf>] throtl_schedule_pending_timer+0x3f/0x210 [ 413.735643] PGD 22c8cf067 PUD 22cb34067 PMD 0 [ 413.735713] Oops: 0000 [#1] SMP ...... This is caused by the following case: blk_throtl_bio throtl_schedule_next_dispatch <= sq is top level one without parent throtl_schedule_pending_timer sq_to_tg(sq)->td->throtl_slice <= sq_to_tg(sq) returns NULL Fix it by using sq_to_td instead of sq_to_tg(sq)->td, which will always return a valid td. Fixes: 297e3d854784 ("blk-throttle: make throtl_slice tunable") Signed-off-by: Joseph Qi <qijiang.qj@alibaba-inc.com> Reviewed-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: force user to configure all settings for io.lowShaohua Li2017-05-221-43/+37
| | | | | | | | | | | | | | Default value of io.low limit is 0. If user doesn't configure the limit, last patch makes cgroup be throttled to very tiny bps/iops, which could stall the system. A cgroup with default settings of io.low limit really means nothing, so we force user to configure all settings, otherwise io.low limit doesn't take effect. With this stragety, default setting of latency/idle isn't important, so just set them to very conservative and safe value. Signed-off-by: Shaohua Li <shli@fb.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: respect 0 bps/iops settings for io.lowShaohua Li2017-05-221-12/+29
| | | | | | | | | | | | | If a cgroup with low limit 0 for both bps/iops, the cgroup's low limit is ignored and we throttle the cgroup with its max limit. In this way, other cgroups with a low limit will not get protected. To fix this, we don't do the exception any more. cgroup will be throttled to a limit 0 if it uese default setting. To avoid completed stall, we give such cgroup tiny IO resources. Signed-off-by: Shaohua Li <shli@fb.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: output some debug info in traceShaohua Li2017-05-221-1/+14
| | | | | | | | These info are important to understand what's happening and help debug. Signed-off-by: Shaohua Li <shli@fb.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add hierarchy support for latency target and idle timeShaohua Li2017-05-221-14/+36
| | | | | | | | | | | | | For idle time, children's setting should not be bigger than parent's. For latency target, children's setting should not be smaller than parent's. The leaf nodes will adjust their settings according to the hierarchy and compare their IO with the settings and do upgrade/downgrade. parents nodes don't need to track their IO latency/idle time. Signed-off-by: Shaohua Li <shli@fb.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: fix unused variable warning with BLK_DEV_THROTTLING_LOW=nJens Axboe2017-04-201-7/+15
| | | | | | | | | | | | | | | | We trigger this warning: block/blk-throttle.c: In function ‘blk_throtl_bio’: block/blk-throttle.c:2042:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable] int ret; ^~~ since we only assign 'ret' if BLK_DEV_THROTTLING_LOW is off, we never check it. Reported-by: Bart Van Assche <bart.vanassche@sandisk.com> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add latency target supportShaohua Li2017-03-281-4/+35
| | | | | | | | | | | | | | | | | | | | | One hard problem adding .low limit is to detect idle cgroup. If one cgroup doesn't dispatch enough IO against its low limit, we must have a mechanism to determine if other cgroups dispatch more IO. We added the think time detection mechanism before, but it doesn't work for all workloads. Here we add a latency based approach. We already have mechanism to calculate latency threshold for each IO size. For every IO dispatched from a cgorup, we compare its latency against its threshold and record the info. If most IO latency is below threshold (in the code I use 75%), the cgroup could be treated idle and other cgroups can dispatch more IO. Currently this latency target check is only for SSD as we can't calcualte the latency target for hard disk. And this is only for cgroup leaf node so far. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add a mechanism to estimate IO latencyShaohua Li2017-03-281-5/+161
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | User configures latency target, but the latency threshold for each request size isn't fixed. For a SSD, the IO latency highly depends on request size. To calculate latency threshold, we sample some data, eg, average latency for request size 4k, 8k, 16k, 32k .. 1M. The latency threshold of each request size will be the sample latency (I'll call it base latency) plus latency target. For example, the base latency for request size 4k is 80us and user configures latency target 60us. The 4k latency threshold will be 80 + 60 = 140us. To sample data, we calculate the order base 2 of rounded up IO sectors. If the IO size is bigger than 1M, it will be accounted as 1M. Since the calculation does round up, the base latency will be slightly smaller than actual value. Also if there isn't any IO dispatched for a specific IO size, we will use the base latency of smaller IO size for this IO size. But we shouldn't sample data at any time. The base latency is supposed to be latency where disk isn't congested, because we use latency threshold to schedule IOs between cgroups. If disk is congested, the latency is higher, using it for scheduling is meaningless. Hence we only do the sampling when block throttling is in the LOW limit, with assumption disk isn't congested in such state. If the assumption isn't true, eg, low limit is too high, calculated latency threshold will be higher. Hard disk is completely different. Latency depends on spindle seek instead of request size. Currently this feature is SSD only, we probably can use a fixed threshold like 4ms for hard disk though. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add interface for per-cgroup target latencyShaohua Li2017-03-281-4/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Here we introduce per-cgroup latency target. The target determines how a cgroup can afford latency increasement. We will use the target latency to calculate a threshold and use it to schedule IO for cgroups. If a cgroup's bandwidth is below its low limit but its average latency is below the threshold, other cgroups can safely dispatch more IO even their bandwidth is higher than their low limits. On the other hand, if the first cgroup's latency is higher than the threshold, other cgroups are throttled to their low limits. So the target latency determines how we efficiently utilize free disk resource without sacifice of worload's IO latency. For example, assume 4k IO average latency is 50us when disk isn't congested. A cgroup sets the target latency to 30us. Then the cgroup can accept 50+30=80us IO latency. If the cgroupt's average IO latency is 90us and its bandwidth is below low limit, other cgroups are throttled to their low limit. If the cgroup's average IO latency is 60us, other cgroups are allowed to dispatch more IO. When other cgroups dispatch more IO, the first cgroup's IO latency will increase. If it increases to 81us, we then throttle other cgroups. User will configure the interface in this way: echo "8:16 rbps=2097152 wbps=max latency=100 idle=200" > io.low latency is in microsecond unit By default, latency target is 0, which means to guarantee IO latency. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: ignore idle cgroup limitShaohua Li2017-03-281-14/+26
| | | | | | | | | Last patch introduces a way to detect idle cgroup. We use it to make upgrade/downgrade decision. And the new algorithm can detect completely idle cgroup too, so we can delete the corresponding code. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add interface to configure idle time thresholdShaohua Li2017-03-281-13/+28
| | | | | | | | | | | Add interface to configure the threshold. The io.low interface will like: echo "8:16 rbps=2097152 wbps=max idle=2000" > io.low idle is in microsecond unit. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add a simple idle detectionShaohua Li2017-03-281-1/+81
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A cgroup gets assigned a low limit, but the cgroup could never dispatch enough IO to cross the low limit. In such case, the queue state machine will remain in LIMIT_LOW state and all other cgroups will be throttled according to low limit. This is unfair for other cgroups. We should treat the cgroup idle and upgrade the state machine to lower state. We also have a downgrade logic. If the state machine upgrades because of cgroup idle (real idle), the state machine will downgrade soon as the cgroup is below its low limit. This isn't what we want. A more complicated case is cgroup isn't idle when queue is in LIMIT_LOW. But when queue gets upgraded to lower state, other cgroups could dispatch more IO and this cgroup can't dispatch enough IO, so the cgroup is below its low limit and looks like idle (fake idle). In this case, the queue should downgrade soon. The key to determine if we should do downgrade is to detect if cgroup is truely idle. Unfortunately it's very hard to determine if a cgroup is real idle. This patch uses the 'think time check' idea from CFQ for the purpose. Please note, the idea doesn't work for all workloads. For example, a workload with io depth 8 has disk utilization 100%, hence think time is 0, eg, not idle. But the workload can run higher bandwidth with io depth 16. Compared to io depth 16, the io depth 8 workload is idle. We use the idea to roughly determine if a cgroup is idle. We treat a cgroup idle if its think time is above a threshold (by default 1ms for SSD and 100ms for HD). The idea is think time above the threshold will start to harm performance. HD is much slower so a longer think time is ok. The patch (and the latter patches) uses 'unsigned long' to track time. We convert 'ns' to 'us' with 'ns >> 10'. This is fast but loses precision, should not a big deal. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: make bandwidth change smoothShaohua Li2017-03-281-3/+54
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When cgroups all reach low limit, cgroups can dispatch more IO. This could make some cgroups dispatch more IO but others not, and even some cgroups could dispatch less IO than their low limit. For example, cg1 low limit 10MB/s, cg2 limit 80MB/s, assume disk maximum bandwidth is 120M/s for the workload. Their bps could something like this: cg1/cg2 bps: T1: 10/80 -> T2: 60/60 -> T3: 10/80 At T1, all cgroups reach low limit, so they can dispatch more IO later. Then cg1 dispatch more IO and cg2 has no room to dispatch enough IO. At T2, cg2 only dispatches 60M/s. Since We detect cg2 dispatches less IO than its low limit 80M/s, we downgrade the queue from LIMIT_MAX to LIMIT_LOW, then all cgroups are throttled to their low limit (T3). cg2 will have bandwidth below its low limit at most time. The big problem here is we don't know the maximum bandwidth of the workload, so we can't make smart decision to avoid the situation. This patch makes cgroup bandwidth change smooth. After disk upgrades from LIMIT_LOW to LIMIT_MAX, we don't allow cgroups use all bandwidth upto their max limit immediately. Their bandwidth limit will be increased gradually to avoid above situation. So above example will became something like: cg1/cg2 bps: 10/80 -> 15/105 -> 20/100 -> 25/95 -> 30/90 -> 35/85 -> 40/80 -> 45/75 -> 22/98 In this way cgroups bandwidth will be above their limit in majority time, this still doesn't fully utilize disk bandwidth, but that's something we pay for sharing. Scale up is linear. The limit scales up 1/2 .low limit every throtl_slice after upgrade. The scale up will stop if the adjusted limit hits .max limit. Scale down is exponential. We cut the scale value half if a cgroup doesn't hit its .low limit. If the scale becomes 0, we then fully downgrade the queue to LIMIT_LOW state. Note this doesn't completely avoid cgroup running under its low limit. The best way to guarantee cgroup doesn't run under its limit is to set max limit. For example, if we set cg1 max limit to 40, cg2 will never run under its low limit. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: detect completed idle cgroupShaohua Li2017-03-281-1/+18
| | | | | | | | | | | | | | | | | cgroup could be assigned a limit, but doesn't dispatch enough IO, eg the cgroup is idle. When this happens, the cgroup doesn't hit its limit, so we can't move the state machine to higher level and all cgroups will be throttled to their lower limit, so we waste bandwidth. Detecting idle cgroup is hard. This patch handles a simple case, a cgroup doesn't dispatch any IO. We ignore such cgroup's limit, so other cgroups can use the bandwidth. Please note this will be replaced with a more sophisticated algorithm later, but this demonstrates the idea how we handle idle cgroups, so I leave it here. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: choose a small throtl_slice for SSDShaohua Li2017-03-281-3/+20
| | | | | | | | | The throtl_slice is 100ms by default. This is a long time for SSD, a lot of IO can run. To make cgroups have smoother throughput, we choose a small value (20ms) for SSD. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: make throtl_slice tunableShaohua Li2017-03-281-22/+57
| | | | | | | | | | | | | | | | | | | throtl_slice is important for blk-throttling. It's called slice internally but it really is a time window blk-throttling samples data. blk-throttling will make decision based on the samplings. An example is bandwidth measurement. A cgroup's bandwidth is measured in the time interval of throtl_slice. A small throtl_slice meanse cgroups have smoother throughput but burn more CPUs. It has 100ms default value, which is not appropriate for all disks. A fast SSD can dispatch a lot of IOs in 100ms. This patch makes it tunable. Since throtl_slice isn't a time slice, the sysfs name 'throttle_sample_time' reflects its character better. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: make sure expire time isn't too bigShaohua Li2017-03-281-0/+11
| | | | | | | | | | | | | | | | | cgroup could be throttled to a limit but when all cgroups cross high limit, queue enters a higher state and so the group should be throttled to a higher limit. It's possible the cgroup is sleeping because of throttle and other cgroups don't dispatch IO any more. In this case, nobody can trigger current downgrade/upgrade logic. To fix this issue, we could either set up a timer to wakeup the cgroup if other cgroups are idle or make sure this cgroup doesn't sleep too long. Setting up a timer means we must change the timer very frequently. This patch chooses the latter. Making cgroup sleep time not too big wouldn't change cgroup bps/iops, but could make it wakeup more frequently, which isn't a big issue because throtl_slice * 8 is already quite big. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add downgrade logicShaohua Li2017-03-281-0/+156
| | | | | | | | | When queue state machine is in LIMIT_MAX state, but a cgroup is below its low limit for some time, the queue should be downgraded to lower state as one cgroup's low limit isn't met. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add upgrade logic for LIMIT_LOW stateShaohua Li2017-03-281-4/+96
| | | | | | | | | | | | | | | | | | | | | | | When queue is in LIMIT_LOW state and all cgroups with low limit cross the bps/iops limitation, we will upgrade queue's state to LIMIT_MAX. To determine if a cgroup exceeds its limitation, we check if the cgroup has pending request. Since cgroup is throttled according to the limit, pending request means the cgroup reaches the limit. If a cgroup has limit set for both read and write, we consider the combination of them for upgrade. The reason is read IO and write IO can interfere with each other. If we do the upgrade based in one direction IO, the other direction IO could be severly harmed. For a cgroup hierarchy, there are two cases. Children has lower low limit than parent. Parent's low limit is meaningless. If children's bps/iops cross low limit, we can upgrade queue state. The other case is children has higher low limit than parent. Children's low limit is meaningless. As long as parent's bps/iops (which is a sum of childrens bps/iops) cross low limit, we can upgrade queue state. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: configure bps/iops limit for cgroup in low limitShaohua Li2017-03-281-2/+18
| | | | | | | | | | | | | | | each queue will have a state machine. Initially queue is in LIMIT_LOW state, which means all cgroups will be throttled according to their low limit. After all cgroups with low limit cross the limit, the queue state gets upgraded to LIMIT_MAX state. For max limit, cgroup will use the limit configured by user. For low limit, cgroup will use the minimal value between low limit and max limit configured by user. If the minimal value is 0, which means the cgroup doesn't configure low limit, we will use max limit to throttle the cgroup and the cgroup is ready to upgrade to LIMIT_MAX Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: add .low interfaceShaohua Li2017-03-281-28/+116
| | | | | | | | | | | | Add low limit for cgroup and corresponding cgroup interface. To be consistent with memcg, we allow users configure .low limit higher than .max limit. But the internal logic always assumes .low limit is lower than .max limit. So we add extra bps/iops_conf fields in throtl_grp for userspace configuration. Old bps/iops fields in throtl_grp will be the actual limit we use for throttling. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: prepare support multiple limitsShaohua Li2017-03-281-40/+70
| | | | | | | | We are going to support low/max limit, each cgroup will have 2 limits after that. This patch prepares for the multiple limits change. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: use U64_MAX/UINT_MAX to replace -1Shaohua Li2017-03-281-16/+16
| | | | | | | clean up the code to avoid using -1 Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* scripts/spelling.txt: add "embeded" pattern and fix typo instancesMasahiro Yamada2017-02-271-1/+1
| | | | | | | | | | | Fix typos and add the following to the scripts/spelling.txt: embeded||embedded Link: http://lkml.kernel.org/r/1481573103-11329-12-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* blk-throttle: Adjust two function calls together with a variable assignmentMarkus Elfring2017-01-231-2/+4
| | | | | | | | | | | | The script "checkpatch.pl" pointed information out like the following. ERROR: do not use assignment in if condition Thus fix the affected source code places. Signed-off-by: Markus Elfring <elfring@users.sourceforge.net> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Jens Axboe <axboe@fb.com>
* block: replace REQ_THROTTLED with a bio flagChristoph Hellwig2016-10-281-5/+5
| | | | | | | | | It's the last bio-only REQ_* flag, and we have space for it in the bio bi_flags field. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Shaun Tancheff <shaun.tancheff@seagate.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: Extend slice if throttle group is not emptyVivek Goyal2016-09-191-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Right now, if slice is expired, we start a new slice. If a bio is queued, we keep on extending slice by throtle_slice interval (100ms). This worked well as long as pending timer function got executed with-in few milli seconds of scheduled time. But looks like with recent changes in timer subsystem, slack can be much longer depending on the expiry time of the scheduled timer. commit 500462a9de65 ("timers: Switch to a non-cascading wheel") This means, by the time timer function gets executed, it is possible the delay from scheduled time is more than 100ms. That means current code will conclude that existing slice has expired and a new one needs to be started. New slice will be 100ms by default and that will not be sufficient to meet rate requirement of group given the bio size and bio will not be dispatched and we will start a new timer function to wait. And when that timer expires, same process will repeat and we will wait again and this can easily be an infinite loop. Solve this issue by starting a new slice only if throttle gropup is empty. If it is not empty, that means there should be an active slice going on. Ideally it should not be expired but given the slack, it is possible that it has expired. Reported-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* block: rename bio bi_rw to bi_opfJens Axboe2016-08-071-4/+4
| | | | | | | | | | | | | Since commit 63a4cc24867d, bio->bi_rw contains flags in the lower portion and the op code in the higher portions. This means that old code that relies on manually setting bi_rw is most likely going to be broken. Instead of letting that brokeness linger, rename the member, to force old and out-of-tree code to break at compile time instead of at runtime. No intended functional changes in this commit. Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: kill unused field nr_undestroyed_grpsHou Tao2016-08-041-5/+0
| | | | | | | | | 'nr_undestroyed_grps' in struct throtl_data was used to count the number of throtl_grp related with throtl_data, but now throtl_grp is tracked by blkcg_gq, so it is useless anymore. Signed-off-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: don't parse cgroup path if trace isn't enabledShaohua Li2016-05-101-3/+2
| | | | | | | if trace isn't enabled, parsing cgroup path just wastes cpu Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* cgroup: replace cgroup_on_dfl() tests in controllers with cgroup_subsys_on_dfl()Tejun Heo2015-09-181-1/+1
| | | | | | | | | | | | | | | | | | | | cgroup_on_dfl() tests whether the cgroup's root is the default hierarchy; however, an individual controller is only interested in whether the controller is attached to the default hierarchy and never tests a cgroup which doesn't belong to the hierarchy that the controller is attached to. This patch replaces cgroup_on_dfl() tests in controllers with faster static_key based cgroup_subsys_on_dfl(). This leaves cgroup core as the only user of cgroup_on_dfl() and the function is moved from the header file to cgroup.c. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Zefan Li <lizefan@huawei.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org>
* blkcg: implement interface for the unified hierarchyTejun Heo2015-08-181-0/+112
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | blkcg interface grew to be the biggest of all controllers and unfortunately most inconsistent too. The interface files are inconsistent with a number of cloes duplicates. Some files have recursive variants while others don't. There's distinction between normal and leaf weights which isn't intuitive and there are a lot of stat knobs which don't make much sense outside of debugging and expose too much implementation details to userland. In the unified hierarchy, everything is always hierarchical and internal nodes can't have tasks rendering the two structural issues twisting the current interface. The interface has to be updated in a significant anyway and this is a good chance to revamp it as a whole. This patch implements blkcg interface for the unified hierarchy. * (from a previous patch) blkcg is identified by "io" instead of "blkio" on the unified hierarchy. Given that the whole interface is updated anyway, the rename shouldn't carry noticeable conversion overhead. * The original interface consisted of 27 files is replaced with the following three files. blkio.stat : per-blkcg stats blkio.weight : per-cgroup and per-cgroup-queue weight settings blkio.max : per-cgroup-queue bps and iops max limits Documentation/cgroups/unified-hierarchy.txt updated accordingly. v2: blkcg_policy->dfl_cftypes wasn't removed on blkcg_policy_unregister() corrupting the cftypes list. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: separate out tg_conf_updated() from tg_set_conf()Tejun Heo2015-08-181-28/+32
| | | | | | | | | | tg_set_conf() is largely consisted of parsing and setting the new config and the follow-up application and propagation. This patch separates out the latter part into tg_conf_updated(). This will be used to implement interface for the unified hierarchy. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: move body parsing from blkg_conf_prep() to its callersTejun Heo2015-08-181-6/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | Currently, blkg_conf_prep() expects input to be of the following form MAJ:MIN NUM and reads the NUM part into blkg_conf_ctx->v. This is quite restrictive and gets in the way in implementing blkcg interface for the unified hierarchy. This patch updates blkg_conf_prep() so that it expects MAJ:MIN BODY_STR where BODY_STR is an arbitrary string. blkg_conf_ctx->v is replaced with ->body which is a char pointer pointing to the start of BODY_STR. Parsing of the body is moved to blkg_conf_prep()'s callers. To allow using, for example, strsep() on blkg_conf_ctx->val, it is a non-const pointer and to accommodate that const is dropped from @input too. This doesn't cause any behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: mark existing cftypes as legacyTejun Heo2015-08-181-2/+2
| | | | | | | | | | | | | | | blkcg is about to grow interface for the unified hierarchy. Add legacy to existing cftypes. * blkcg_policy->cftypes -> blkcg_policy->legacy_cftypes * blk-cgroup.c:blkcg_files -> blkcg_legacy_files * cfq-iosched.c:cfq_blkcg_files -> cfq_blkcg_legacy_files * blk-throttle.c:throtl_files -> throtl_legacy_files Pure renames. No functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: move io_service_bytes and io_serviced stats into blkcg_gqTejun Heo2015-08-181-67/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, both cfq-iosched and blk-throttle keep track of io_service_bytes and io_serviced stats. While keeping track of them separately may be useful during development, it doesn't make much sense otherwise. Also, blk-throttle was counting bio's as IOs while cfq-iosched request's, which is more confusing than informative. This patch adds ->stat_bytes and ->stat_ios to blkg (blkcg_gq), removes the counterparts from cfq-iosched and blk-throttle and let them print from the common blkg counters. The common counters are incremented during bio issue in blkcg_bio_issue_check(). The outputs are still filtered by whether the policy has blkg_policy_data on a given blkg, so cfq's output won't show up if it has never been used for a given blkg. The only times when the outputs would differ significantly are when policies are attached on the fly or elevators are switched back and forth. Those are quite exceptional operations and I don't think they warrant keeping separate counters. v3: Update blkio-controller.txt accordingly. v2: Account IOs during bio issues instead of request completions so that bio-based drivers can be handled the same way. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: make blkcg_[rw]stat per-cpuTejun Heo2015-08-181-61/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | blkcg_[rw]stat are used as stat counters for blkcg policies. It isn't per-cpu by itself and blk-throttle makes it per-cpu by wrapping around it. This patch makes blkcg_[rw]stat per-cpu and drop the ad-hoc per-cpu wrapping in blk-throttle. * blkg_[rw]stat->cnt is replaced with cpu_cnt which is struct percpu_counter. This makes syncp unnecessary as remote accesses are handled by percpu_counter itself. * blkg_[rw]stat_init() can now fail due to percpu allocation failure and thus are updated to return int. * percpu_counters need explicit freeing. blkg_[rw]stat_exit() added. * As blkg_rwstat->cpu_cnt[] can't be read directly anymore, reading and summing results are stored in ->aux_cnt[] instead. * Custom per-cpu stat implementation in blk-throttle is removed. This makes all blkcg stat counters per-cpu without complicating policy implmentations. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: consolidate blkg creation in blkcg_bio_issue_check()Tejun Heo2015-08-181-66/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | blkg (blkcg_gq) currently is created by blkcg policies invoking blkg_lookup_create() which ends up repeating about the same code in different policies. Theoretically, this can avoid the overhead of looking and/or creating blkg's if blkcg is enabled but no policy is in use; however, the cost of blkg lookup / creation is very low especially if only the root blkcg is in use which is highly likely if no blkcg policy is in active use - it boils down to a single very predictable conditional and surrounding RCU protection. This patch consolidates blkg creation to a new function blkcg_bio_issue_check() which is called during bio issue from generic_make_request_checks(). blkcg_bio_issue_check() is now the only function which tries to create missing blkg's. The subsequent policy and request_list operations just perform blkg_lookup() and if missing falls back to the root. * blk_get_rl() no longer tries to create blkg. It uses blkg_lookup() instead of blkg_lookup_create(). * blk_throtl_bio() is now called from blkcg_bio_issue_check() with rcu read locked and blkg already looked up. Both throtl_lookup_tg() and throtl_lookup_create_tg() are dropped. * cfq is similarly updated. cfq_lookup_create_cfqg() is replaced with cfq_lookup_cfqg()which uses blkg_lookup(). This consolidates blkg handling and avoids unnecessary blkg creation retries under memory pressure. In addition, this provides a common bio entry point into blkcg where things like common accounting can be performed. v2: Build fixes for !CONFIG_CFQ_GROUP_IOSCHED and !CONFIG_BLK_DEV_THROTTLING. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Arianna Avanzini <avanzini.arianna@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: improve queue bypass handlingTejun Heo2015-08-181-3/+4
| | | | | | | | | | | | | | | | | If a queue is bypassing, all blkcg policies should become noops but blk-throttle wasn't. It only became noop if the queue was dying. While this wouldn't lead to an oops as falling back to the root blkg is safe in this case, this can be a bit surprising - a bypassing queue could still be applying throttle limits. Fix it by removing blk_queue_dying() test in throtl_lookup_create_tg() and testing blk_queue_bypass() in blk_throtl_bio() and bypassing before doing anything else. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Arianna Avanzini <avanzini.arianna@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: move root blkg lookup optimization from throtl_lookup_tg() to ↵Tejun Heo2015-08-181-7/+0
| | | | | | | | | | | | | | | __blkg_lookup() Currently, both throttle and cfq policies implement their own root blkg (blkcg_gq) lookup fast path. This patch moves root blkg optimization from throtl_lookup_tg() to __blkg_lookup(). cfq-iosched currently doesn't use blkg_lookup() but will be converted and drop the optimization too. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Arianna Avanzini <avanzini.arianna@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: make blkcg_policy methods take a pointer to blkcg_policy_dataTejun Heo2015-08-181-6/+7
| | | | | | | | | | | | | | | | | The newly added ->pd_alloc_fn() and ->pd_free_fn() deal with pd (blkg_policy_data) while the older ones use blkg (blkcg_gq). As using blkg doesn't make sense for ->pd_alloc_fn() and after allocation pd can always be mapped to blkg and given that these are policy-specific methods, it makes sense to converge on pd. This patch makes all methods deal with pd instead of blkg. Most conversions are trivial. In blk-cgroup.c, a couple method invocation sites now test whether pd exists instead of policy state for consistency. This shouldn't cause any behavioral differences. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: clean up blkg_policy_data alloc/init/exit/free methodsTejun Heo2015-08-181-37/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | With the recent addition of alloc and free methods, things became messier. This patch reorganizes them according to the followings. * ->pd_alloc_fn() Responsible for allocation and static initializations - the ones which can be done independent of where the pd might be attached. * ->pd_init_fn() Initializations which require the knowledge of where the pd is attached. * ->pd_free_fn() The counter part of pd_alloc_fn(). Static de-init and freeing. This leaves ->pd_exit_fn() without any users. Removed. While at it, collapse an one liner function throtl_pd_exit(), which has only one user, into its user. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: remove asynchrnous percpu stats allocation mechanismTejun Heo2015-08-181-87/+25
| | | | | | | | | | | | | | | | | | | Because percpu allocator couldn't do non-blocking allocations, blk-throttle was forced to implement an ad-hoc asynchronous allocation mechanism for its percpu stats for cases where blkg's (blkcg_gq's) are allocated from an IO path without sleepable context. Now that percpu allocator can handle gfp_mask and blkg_policy_data alloc / free are handled by policy methods, the ad-hoc asynchronous allocation mechanism can be replaced with direct allocation from tg_stats_alloc_fn(). Rit it out. This ensures that an active throtl_grp always has valid non-NULL ->stats_cpu. Remove checks on it. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: replace blkcg_policy->pd_size with ->pd_alloc/free_fn() methodsTejun Heo2015-08-181-1/+12
| | | | | | | | | | | | | | | | | | | | | | | A blkg (blkcg_gq) represents the relationship between a cgroup and request_queue. Each active policy has a pd (blkg_policy_data) on each blkg. The pd's were allocated by blkcg core and each policy could request to allocate extra space at the end by setting blkcg_policy->pd_size larger than the size of pd. This is a bit unusual but was done this way mostly to simplify error handling and all the existing use cases could be handled this way; however, this is becoming too restrictive now that percpu memory can be allocated without blocking. This introduces two new mandatory blkcg_policy methods - pd_alloc_fn() and pd_free_fn() - which are used to allocate and release pd for a given policy. As pd allocation is now done from policy side, it can simply allocate a larger area which embeds pd at the beginning. This change makes ->pd_size pointless. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blkcg: move block/blk-cgroup.h to include/linux/blk-cgroup.hTejun Heo2015-06-021-1/+1
| | | | | | | | | | cgroup aware writeback support will require exposing some of blkcg details. In preprataion, move block/blk-cgroup.h to include/linux/blk-cgroup.h. This patch is pure file move. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
* blk-throttle: check stats_cpu before reading it from sysfsThadeu Lima de Souza Cascardo2015-02-201-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When reading blkio.throttle.io_serviced in a recently created blkio cgroup, it's possible to race against the creation of a throttle policy, which delays the allocation of stats_cpu. Like other functions in the throttle code, just checking for a NULL stats_cpu prevents the following oops caused by that race. [ 1117.285199] Unable to handle kernel paging request for data at address 0x7fb4d0020 [ 1117.285252] Faulting instruction address: 0xc0000000003efa2c [ 1137.733921] Oops: Kernel access of bad area, sig: 11 [#1] [ 1137.733945] SMP NR_CPUS=2048 NUMA PowerNV [ 1137.734025] Modules linked in: bridge stp llc kvm_hv kvm binfmt_misc autofs4 [ 1137.734102] CPU: 3 PID: 5302 Comm: blkcgroup Not tainted 3.19.0 #5 [ 1137.734132] task: c000000f1d188b00 ti: c000000f1d210000 task.ti: c000000f1d210000 [ 1137.734167] NIP: c0000000003efa2c LR: c0000000003ef9f0 CTR: c0000000003ef980 [ 1137.734202] REGS: c000000f1d213500 TRAP: 0300 Not tainted (3.19.0) [ 1137.734230] MSR: 9000000000009032 <SF,HV,EE,ME,IR,DR,RI> CR: 42008884 XER: 20000000 [ 1137.734325] CFAR: 0000000000008458 DAR: 00000007fb4d0020 DSISR: 40000000 SOFTE: 0 GPR00: c0000000003ed3a0 c000000f1d213780 c000000000c59538 0000000000000000 GPR04: 0000000000000800 0000000000000000 0000000000000000 0000000000000000 GPR08: ffffffffffffffff 00000007fb4d0020 00000007fb4d0000 c000000000780808 GPR12: 0000000022000888 c00000000fdc0d80 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 000001003e120200 c000000f1d5b0cc0 0000000000000200 0000000000000000 GPR24: 0000000000000001 c000000000c269e0 0000000000000020 c000000f1d5b0c80 GPR28: c000000000ca3a08 c000000000ca3dec c000000f1c667e00 c000000f1d213850 [ 1137.734886] NIP [c0000000003efa2c] .tg_prfill_cpu_rwstat+0xac/0x180 [ 1137.734915] LR [c0000000003ef9f0] .tg_prfill_cpu_rwstat+0x70/0x180 [ 1137.734943] Call Trace: [ 1137.734952] [c000000f1d213780] [d000000005560520] 0xd000000005560520 (unreliable) [ 1137.734996] [c000000f1d2138a0] [c0000000003ed3a0] .blkcg_print_blkgs+0xe0/0x1a0 [ 1137.735039] [c000000f1d213960] [c0000000003efb50] .tg_print_cpu_rwstat+0x50/0x70 [ 1137.735082] [c000000f1d2139e0] [c000000000104b48] .cgroup_seqfile_show+0x58/0x150 [ 1137.735125] [c000000f1d213a70] [c0000000002749dc] .kernfs_seq_show+0x3c/0x50 [ 1137.735161] [c000000f1d213ae0] [c000000000218630] .seq_read+0xe0/0x510 [ 1137.735197] [c000000f1d213bd0] [c000000000275b04] .kernfs_fop_read+0x164/0x200 [ 1137.735240] [c000000f1d213c80] [c0000000001eb8e0] .__vfs_read+0x30/0x80 [ 1137.735276] [c000000f1d213cf0] [c0000000001eb9c4] .vfs_read+0x94/0x1b0 [ 1137.735312] [c000000f1d213d90] [c0000000001ebb38] .SyS_read+0x58/0x100 [ 1137.735349] [c000000f1d213e30] [c000000000009218] syscall_exit+0x0/0x98 [ 1137.735383] Instruction dump: [ 1137.735405] 7c6307b4 7f891800 409d00b8 60000000 60420000 3d420004 392a63b0 786a1f24 [ 1137.735471] 7d49502a e93e01c8 7d495214 7d2ad214 <7cead02a> e9090008 e9490010 e9290018 And here is one code that allows to easily reproduce this, although this has first been found by running docker. void run(pid_t pid) { int n; int status; int fd; char *buffer; buffer = memalign(BUFFER_ALIGN, BUFFER_SIZE); n = snprintf(buffer, BUFFER_SIZE, "%d\n", pid); fd = open(CGPATH "/test/tasks", O_WRONLY); write(fd, buffer, n); close(fd); if (fork() > 0) { fd = open("/dev/sda", O_RDONLY | O_DIRECT); read(fd, buffer, 512); close(fd); wait(&status); } else { fd = open(CGPATH "/test/blkio.throttle.io_serviced", O_RDONLY); n = read(fd, buffer, BUFFER_SIZE); close(fd); } free(buffer); exit(0); } void test(void) { int status; mkdir(CGPATH "/test", 0666); if (fork() > 0) wait(&status); else run(getpid()); rmdir(CGPATH "/test"); } int main(int argc, char **argv) { int i; for (i = 0; i < NR_TESTS; i++) test(); return 0; } Reported-by: Ricardo Marin Matinata <rmm@br.ibm.com> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@fb.com>
* cgroup: remove sane_behavior support on non-default hierarchiesTejun Heo2014-07-091-3/+3
| | | | | | | | | | | | | | | | | | | | | | sane_behavior has been used as a development vehicle for the default unified hierarchy. Now that the default hierarchy is in place, the flag became redundant and confusing as its usage is allowed on all hierarchies. There are gonna be either the default hierarchy or legacy ones. Let's make that clear by removing sane_behavior support on non-default hierarchies. This patch replaces cgroup_sane_behavior() with cgroup_on_dfl(). The comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of cgroup_on_dfl() with sane_behavior specific part dropped. On the default and legacy hierarchies w/o sane_behavior, this shouldn't cause any behavior differences. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz>
* Merge branch 'for-3.16' of ↵Linus Torvalds2014-06-091-16/+16
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: "A lot of activities on cgroup side. Heavy restructuring including locking simplification took place to improve the code base and enable implementation of the unified hierarchy, which currently exists behind a __DEVEL__ mount option. The core support is mostly complete but individual controllers need further work. To explain the design and rationales of the the unified hierarchy Documentation/cgroups/unified-hierarchy.txt is added. Another notable change is css (cgroup_subsys_state - what each controller uses to identify and interact with a cgroup) iteration update. This is part of continuing updates on css object lifetime and visibility. cgroup started with reference count draining on removal way back and is now reaching a point where csses behave and are iterated like normal refcnted objects albeit with some complexities to allow distinguishing the state where they're being deleted. The css iteration update isn't taken advantage of yet but is planned to be used to simplify memcg significantly" * 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits) cgroup: disallow disabled controllers on the default hierarchy cgroup: don't destroy the default root cgroup: disallow debug controller on the default hierarchy cgroup: clean up MAINTAINERS entries cgroup: implement css_tryget() device_cgroup: use css_has_online_children() instead of has_children() cgroup: convert cgroup_has_live_children() into css_has_online_children() cgroup: use CSS_ONLINE instead of CGRP_DEAD cgroup: iterate cgroup_subsys_states directly cgroup: introduce CSS_RELEASED and reduce css iteration fallback window cgroup: move cgroup->serial_nr into cgroup_subsys_state cgroup: link all cgroup_subsys_states in their sibling lists cgroup: move cgroup->sibling and ->children into cgroup_subsys_state cgroup: remove cgroup->parent device_cgroup: remove direct access to cgroup->children memcg: update memcg_has_children() to use css_next_child() memcg: remove tasks/children test from mem_cgroup_force_empty() cgroup: remove css_parent() cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css cgroup: use cgroup->self.refcnt for cgroup refcnting ...
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