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2020-10-08block: Remove redundant 'return' statementBaolin Wang1-1/+1
Remove redundant 'return' statement for 'void' functions. Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-07-01blk-iolatency: only call ktime_get() if neededHongnan Li1-1/+2
ktime_to_ns(ktime_get()), which is expensive, does not need to be called if blk_iolatency_enabled() return false in blkcg_iolatency_done_bio(). Postponing ktime_to_ns(ktime_get()) execution reduces the CPU usage when blk_iolatency is disabled. Signed-off-by: Hongnan Li <hongnan.li@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-29blkcg: s/RQ_QOS_CGROUP/RQ_QOS_LATENCY/Tejun Heo1-1/+1
io.weight is gonna be another rq_qos cgroup mechanism. Let's rename RQ_QOS_CGROUP which is being used by io.latency to RQ_QOS_LATENCY in preparation. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-29blkcg: pass @q and @blkcg into blkcg_pol_alloc_pd_fn()Tejun Heo1-2/+4
Instead of @node, pass in @q and @blkcg so that the alloc function has more context. This doesn't cause any behavior change and will be used by io.weight implementation. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-16blkcg: allow blkcg_policy->pd_stat() to print non-debug info tooTejun Heo1-0/+3
Currently, ->pd_stat() is called only when moduleparam blkcg_debug_stats is set which prevents it from printing non-debug policy-specific statistics. Let's move debug testing down so that ->pd_stat() can print non-debug stat too. This patch doesn't cause any visible behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-06blk-iolatency: fix STS_AGAIN handlingDennis Zhou1-37/+14
The iolatency controller is based on rq_qos. It increments on rq_qos_throttle() and decrements on either rq_qos_cleanup() or rq_qos_done_bio(). a3fb01ba5af0 fixes the double accounting issue where blk_mq_make_request() may call both rq_qos_cleanup() and rq_qos_done_bio() on REQ_NO_WAIT. So checking STS_AGAIN prevents the double decrement. The above works upstream as the only way we can get STS_AGAIN is from blk_mq_get_request() failing. The STS_AGAIN handling isn't a real problem as bio_endio() skipping only happens on reserved tag allocation failures which can only be caused by driver bugs and already triggers WARN. However, the fix creates a not so great dependency on how STS_AGAIN can be propagated. Internally, we (Facebook) carry a patch that kills read ahead if a cgroup is io congested or a fatal signal is pending. This combined with chained bios progagate their bi_status to the parent is not already set can can cause the parent bio to not clean up properly even though it was successful. This consequently leaks the inflight counter and can hang all IOs under that blkg. To nip the adverse interaction early, this removes the rq_qos_cleanup() callback in iolatency in favor of cleaning up always on the rq_qos_done_bio() path. Fixes: a3fb01ba5af0 ("blk-iolatency: only account submitted bios") Debugged-by: Tejun Heo <tj@kernel.org> Debugged-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-20blk-iolatency: only account submitted biosDennis Zhou1-0/+4
As is, iolatency recognizes done_bio and cleanup as ending paths. If a request is marked REQ_NOWAIT and fails to get a request, the bio is cleaned up via rq_qos_cleanup() and ended in bio_wouldblock_error(). This results in underflowing the inflight counter. Fix this by only accounting bios that were actually submitted. Signed-off-by: Dennis Zhou <dennis@kernel.org> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-15blk-iolatency: clear use_delay when io.latency is set to zeroTejun Heo1-1/+3
If use_delay was non-zero when the latency target of a cgroup was set to zero, it will stay stuck until io.latency is enabled on the cgroup again. This keeps readahead disabled for the cgroup impacting performance negatively. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Josef Bacik <jbacik@fb.com> Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-05-01block: add SPDX tags to block layer files missing licensing informationChristoph Hellwig1-0/+1
Various block layer files do not have any licensing information at all. Add SPDX tags for the default kernel GPLv2 license to those. Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-03-20blk-iolatency: #include "blk.h"Bart Van Assche1-0/+1
This patch avoids that the following warning is reported when building with W=1: block/blk-iolatency.c:734:5: warning: no previous prototype for 'blk_iolatency_init' [-Wmissing-prototypes] Cc: Josef Bacik <jbacik@fb.com> Fixes: d70675121546 ("block: introduce blk-iolatency io controller") # v4.19 Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-08Blk-iolatency: warn on negative inflight IO counterLiu Bo1-1/+3
This is to catch any unexpected negative value of inflight IO counter. Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-08blk-iolatency: fix IO hang due to negative inflight counterLiu Bo1-7/+45
Our test reported the following stack, and vmcore showed that ->inflight counter is -1. [ffffc9003fcc38d0] __schedule at ffffffff8173d95d [ffffc9003fcc3958] schedule at ffffffff8173de26 [ffffc9003fcc3970] io_schedule at ffffffff810bb6b6 [ffffc9003fcc3988] blkcg_iolatency_throttle at ffffffff813911cb [ffffc9003fcc3a20] rq_qos_throttle at ffffffff813847f3 [ffffc9003fcc3a48] blk_mq_make_request at ffffffff8137468a [ffffc9003fcc3b08] generic_make_request at ffffffff81368b49 [ffffc9003fcc3b68] submit_bio at ffffffff81368d7d [ffffc9003fcc3bb8] ext4_io_submit at ffffffffa031be00 [ext4] [ffffc9003fcc3c00] ext4_writepages at ffffffffa03163de [ext4] [ffffc9003fcc3d68] do_writepages at ffffffff811c49ae [ffffc9003fcc3d78] __filemap_fdatawrite_range at ffffffff811b6188 [ffffc9003fcc3e30] filemap_write_and_wait_range at ffffffff811b6301 [ffffc9003fcc3e60] ext4_sync_file at ffffffffa030cee8 [ext4] [ffffc9003fcc3ea8] vfs_fsync_range at ffffffff8128594b [ffffc9003fcc3ee8] do_fsync at ffffffff81285abd [ffffc9003fcc3f18] sys_fsync at ffffffff81285d50 [ffffc9003fcc3f28] do_syscall_64 at ffffffff81003c04 [ffffc9003fcc3f50] entry_SYSCALL_64_after_swapgs at ffffffff81742b8e The ->inflight counter may be negative (-1) if 1) blk-iolatency was disabled when the IO was issued, 2) blk-iolatency was enabled before this IO reached its endio, 3) the ->inflight counter is decreased from 0 to -1 in endio() In fact the hang can be easily reproduced by the below script, H=/sys/fs/cgroup/unified/ P=/sys/fs/cgroup/unified/test echo "+io" > $H/cgroup.subtree_control mkdir -p $P echo $$ > $P/cgroup.procs xfs_io -f -d -c "pwrite 0 4k" /dev/sdg echo "`cat /sys/block/sdg/dev` target=1000000" > $P/io.latency xfs_io -f -d -c "pwrite 0 4k" /dev/sdg This fixes the problem by freezing the queue so that while enabling/disabling iolatency, there is no inflight rq running. Note that quiesce_queue is not needed as this only updating iolatency configuration about which dispatching request_queue doesn't care. Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-17block: fix blk-iolatency accounting underflowDennis Zhou1-1/+1
The blk-iolatency controller measures the time from rq_qos_throttle() to rq_qos_done_bio() and attributes this time to the first bio that needs to create the request. This means if a bio is plug-mergeable or bio-mergeable, it gets to bypass the blk-iolatency controller. The recent series [1], to tag all bios w/ blkgs undermined how iolatency was determining which bios it was charging and should process in rq_qos_done_bio(). Because all bios are being tagged, this caused the atomic_t for the struct rq_wait inflight count to underflow and result in a stall. This patch adds a new flag BIO_TRACKED to let controllers know that a bio is going through the rq_qos path. blk-iolatency now checks if this flag is set to see if it should process the bio in rq_qos_done_bio(). Overloading BLK_QUEUE_ENTERED works, but makes the flag rules confusing. BIO_THROTTLED was another candidate, but the flag is set for all bios that have gone through blk-throttle code. Overloading a flag comes with the burden of making sure that when either implementation changes, a change in setting rules for one doesn't cause a bug in the other. So here, we unfortunately opt for adding a new flag. [1] https://lore.kernel.org/lkml/20181205171039.73066-1-dennis@kernel.org/ Fixes: 5cdf2e3fea5e ("blkcg: associate blkg when associating a device") Signed-off-by: Dennis Zhou <dennis@kernel.org> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08block: convert io-latency to use rq_qos_waitJosef Bacik1-23/+8
Now that we have this common helper, convert io-latency over to use it as well. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: rename blkg_try_get() to blkg_tryget()Dennis Zhou1-1/+1
blkg reference counting now uses percpu_ref rather than atomic_t. Let's make this consistent with css_tryget. This renames blkg_try_get to blkg_tryget and now returns a bool rather than the blkg or %NULL. Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: consolidate bio_issue_init() to be a part of coreDennis Zhou1-2/+0
bio_issue_init among other things initializes the timestamp for an IO. Rather than have this logic handled by policies, this consolidates it to be on the init paths (normal, clone, bounce clone). Signed-off-by: Dennis Zhou <dennis@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: associate blkg when associating a deviceDennis Zhou1-3/+1
Previously, blkg association was handled by controller specific code in blk-throttle and blk-iolatency. However, because a blkg represents a relationship between a blkcg and a request_queue, it makes sense to keep the blkg->q and bio->bi_disk->queue consistent. This patch moves association into the bio_set_dev macro(). This should cover the majority of cases where the device is set/changed keeping the two pointers consistent. Fallback code is added to blkcg_bio_issue_check() to catch any missing paths. Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: introduce common blkg association logicDennis Zhou1-8/+2
There are 3 ways blkg association can happen: association with the current css, with the page css (swap), or from the wbc css (writeback). This patch handles how association is done for the first case where we are associating bsaed on the current css. If there is already a blkg associated, the css will be reused and association will be redone as the request_queue may have changed. Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: convert blkg_lookup_create() to find closest blkgDennis Zhou1-12/+2
There are several scenarios where blkg_lookup_create() can fail such as the blkcg dying, request_queue is dying, or simply being OOM. Most handle this by simply falling back to the q->root_blkg and calling it a day. This patch implements the notion of closest blkg. During blkg_lookup_create(), if it fails to create, return the closest blkg found or the q->root_blkg. blkg_try_get_closest() is introduced and used during association so a bio is always attached to a blkg. Signed-off-by: Dennis Zhou <dennis@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: update blkg_lookup_create() to do lockingDennis Zhou1-1/+1
To know when to create a blkg, the general pattern is to do a blkg_lookup() and if that fails, lock and do the lookup again, and if that fails finally create. It doesn't make much sense for everyone who wants to do creation to write this themselves. This changes blkg_lookup_create() to do locking and implement this pattern. The old blkg_lookup_create() is renamed to __blkg_lookup_create(). If a call site wants to do its own error handling or already owns the queue lock, they can use __blkg_lookup_create(). This will be used in upcoming patches. Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-08blkcg: fix ref count issue with bio_blkcg() using task_cssDennis Zhou1-1/+1
The bio_blkcg() function turns out to be inconsistent and consequently dangerous to use. The first part returns a blkcg where a reference is owned by the bio meaning it does not need to be rcu protected. However, the third case, the last line, is problematic: return css_to_blkcg(task_css(current, io_cgrp_id)); This can race against task migration and the cgroup dying. It is also semantically different as it must be called rcu protected and is susceptible to failure when trying to get a reference to it. This patch adds association ahead of calling bio_blkcg() rather than after. This makes association a required and explicit step along the code paths for calling bio_blkcg(). In blk-iolatency, association is moved above the bio_blkcg() call to ensure it will not return %NULL. BFQ uses the old bio_blkcg() function, but I do not want to address it in this series due to the complexity. I have created a private version documenting the inconsistency and noting not to use it. Signed-off-by: Dennis Zhou <dennis@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-15block: remove the queue_lock indirectionChristoph Hellwig1-2/+2
With the legacy request path gone there is no good reason to keep queue_lock as a pointer, we can always use the embedded lock now. Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Fixed floppy and blk-cgroup missing conversions and half done edits. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-15block: remove the unused lock argument to rq_qos_throttleChristoph Hellwig1-18/+6
Unused now that the legacy request path is gone. Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-02Merge tag 'for-linus-20181102' of git://git.kernel.dk/linux-blockLinus Torvalds1-2/+24
Pull block layer fixes from Jens Axboe: "The biggest part of this pull request is the revert of the blkcg cleanup series. It had one fix earlier for a stacked device issue, but another one was reported. Rather than play whack-a-mole with this, revert the entire series and try again for the next kernel release. Apart from that, only small fixes/changes. Summary: - Indentation fixup for mtip32xx (Colin Ian King) - The blkcg cleanup series revert (Dennis Zhou) - Two NVMe fixes. One fixing a regression in the nvme request initialization in this merge window, causing nvme-fc to not work. The other is a suspend/resume p2p resource issue (James, Keith) - Fix sg discard merge, allowing us to merge in cases where we didn't before (Jianchao Wang) - Call rq_qos_exit() after the queue is frozen, preventing a hang (Ming) - Fix brd queue setup, fixing an oops if we fail setting up all devices (Ming)" * tag 'for-linus-20181102' of git://git.kernel.dk/linux-block: nvme-pci: fix conflicting p2p resource adds nvme-fc: fix request private initialization blkcg: revert blkcg cleanups series block: brd: associate with queue until adding disk block: call rq_qos_exit() after queue is frozen mtip32xx: clean an indentation issue, remove extraneous tabs block: fix the DISCARD request merge
2018-11-02blkcg: revert blkcg cleanups seriesDennis Zhou1-2/+24
This reverts a series committed earlier due to null pointer exception bug report in [1]. It seems there are edge case interactions that I did not consider and will need some time to understand what causes the adverse interactions. The original series can be found in [2] with a follow up series in [3]. [1] https://www.spinics.net/lists/cgroups/msg20719.html [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/ [3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/ This reverts the following commits: d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae, f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef, a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53 Signed-off-by: Dennis Zhou <dennis@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-10-27sched: loadavg: consolidate LOAD_INT, LOAD_FRAC, CALC_LOADJohannes Weiner1-3/+5
There are several definitions of those functions/macros in places that mess with fixed-point load averages. Provide an official version. [akpm@linux-foundation.org: fix missed conversion in block/blk-iolatency.c] Link: http://lkml.kernel.org/r/20180828172258.3185-5-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Suren Baghdasaryan <surenb@google.com> Tested-by: Daniel Drake <drake@endlessm.com> Cc: Christopher Lameter <cl@linux.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <jweiner@fb.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Enderborg <peter.enderborg@sony.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vinayak Menon <vinmenon@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-09-28blk-iolatency: keep track of previous windows statsJosef Bacik1-7/+13
We apply a smoothing to the scale changes in order to keep sawtoothy behavior from occurring. However our window for checking if we've missed our target can sometimes be lower than the smoothing interval (500ms), especially on faster drives like ssd's. In order to deal with this keep track of the running tally of the previous intervals that we threw away because we had already done a scale event recently. This is needed for the ssd case as these low latency drives will have bursts of latency, and if it happens to be ok for the window that directly follows the opening of the scale window we could unthrottle when previous windows we were missing our target. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-28blk-iolatency: use a percentile approache for ssd'sJosef Bacik1-34/+145
We use an average latency approach for determining if we're missing our latency target. This works well for rotational storage where we have generally consistent latencies, but for ssd's and other low latency devices you have more of a spikey behavior, which means we often won't throttle misbehaving groups because a lot of IO completes at drastically faster times than our latency target. Instead keep track of how many IO's miss our target and how many IO's are done in our time window. If the p(90) latency is above our target then we know we need to throttle. With this change in place we are seeing the same throttling behavior with our testcase on ssd's as we see with rotational drives. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-28blk-iolatency: deal with small samplesJosef Bacik1-1/+1
There is logic to keep cgroups that haven't done a lot of IO in the most recent scale window from being punished for over-active higher priority groups. However for things like ssd's where the windows are pretty short we'll end up with small numbers of samples, so 5% of samples will come out to 0 if there aren't enough. Make the floor 1 sample to keep us from improperly bailing out of scaling down. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-28blk-iolatency: deal with nr_requests == 1Josef Bacik1-1/+1
Hitting the case where blk_queue_depth() returned 1 uncovered the fact that iolatency doesn't actually handle this case properly, it simply doesn't scale down anybody. For this case we should go straight into applying the time delay, which we weren't doing. Since we already limit the floor at 1 request this if statement is not needed, and this allows us to set our depth to 1 which allows us to apply the delay if needed. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-28blk-iolatency: use q->nr_requests directlyJosef Bacik1-3/+3
We were using blk_queue_depth() assuming that it would return nr_requests, but we hit a case in production on drives that had to have NCQ turned off in order for them to not shit the bed which resulted in a qd of 1, even though the nr_requests was much larger. iolatency really only cares about requests we are allowed to queue up, as any io that get's onto the request list is going to be serviced soonish, so we want to be throttling before the bio gets onto the request list. To make iolatency work as expected, simply use q->nr_requests instead of blk_queue_depth() as that is what we actually care about. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-22blkcg: rename blkg_try_get to blkg_trygetDennis Zhou (Facebook)1-1/+1
blkg reference counting now uses percpu_ref rather than atomic_t. Let's make this consistent with css_tryget. This renames blkg_try_get to blkg_tryget and now returns a bool rather than the blkg or NULL. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-22blkcg: consolidate bio_issue_init to be a part of coreDennis Zhou (Facebook)1-2/+0
bio_issue_init among other things initializes the timestamp for an IO. Rather than have this logic handled by policies, this consolidates it to be on the init paths (normal, clone, bounce clone). Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-22blkcg: always associate a bio with a blkgDennis Zhou (Facebook)1-22/+2
Previously, blkg's were only assigned as needed by blk-iolatency and blk-throttle. bio->css was also always being associated while blkg was being looked up and then thrown away in blkcg_bio_issue_check. This patch begins the cleanup of bio->css and bio->bi_blkg by always associating a blkg in blkcg_bio_issue_check. This tries to create the blkg, but if it is not possible, falls back to using the root_blkg of the request_queue. Therefore, a bio will always be associated with a blkg. The duplicate association logic is removed from blk-throttle and blk-iolatency. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-22blkcg: update blkg_lookup_create to do lockingDennis Zhou (Facebook)1-1/+1
To know when to create a blkg, the general pattern is to do a blkg_lookup and if that fails, lock and then do a lookup again and if that fails finally create. It doesn't make much sense for everyone who wants to do creation to write this themselves. This changes blkg_lookup_create to do locking and implement this pattern. The old blkg_lookup_create is renamed to __blkg_lookup_create. If a call site wants to do its own error handling or already owns the queue lock, they can use __blkg_lookup_create. This will be used in upcoming patches. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-22blkcg: fix ref count issue with bio_blkcg using task_cssDennis Zhou (Facebook)1-1/+1
The accessor function bio_blkcg either returns the blkcg associated with the bio or finds one in the current context. This can cause an issue when trying to associate a bio with a blkcg. Particularly, it's the third case that is problematic: return css_to_blkcg(task_css(current, io_cgrp_id)); As the above may race against task migration and the cgroup exiting, it is not always ok to take a reference on the blkcg returned from bio_blkcg. This patch adds association ahead of calling bio_blkcg rather than after. This makes association a required and explicit step along the code paths for calling bio_blkcg. blk_get_rl is modified as well to get a reference to the blkcg it may use and blk_put_rl will always put the reference back. Association is also moved above the bio_blkcg call to ensure it will not return NULL in blk-iolatency. BFQ and CFQ utilize this flaw, but due to the complexity, I do not want to address this in this series. I've created a private version of the function with notes not to use it describing the flaw. Hopefully soon, that code can be cleaned up. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-09-14blk-iolatency: remove set but not used variables 'changed' and 'blkiolat'YueHaibing1-5/+0
Fixes gcc '-Wunused-but-set-variable' warning: block/blk-iolatency.c: In function 'scale_change': block/blk-iolatency.c:301:7: warning: variable 'changed' set but not used [-Wunused-but-set-variable] block/blk-iolatency.c: In function 'iolatency_set_limit': block/blk-iolatency.c:765:24: warning: variable 'blkiolat' set but not used [-Wunused-but-set-variable] Signed-off-by: YueHaibing <yuehaibing@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-08-02block: make iolatency avg_lat exponentially decayDennis Zhou (Facebook)1-15/+45
Currently, avg_lat is calculated by accumulating the mean of every window in a long running cumulative average. As time goes on, the metric becomes less and less useful due to the accumulated history. This patch reuses the same calculation done in load averages to make the avg_lat metric more lively. Unlike load averages, the avg only advances when a window elapses (due to an io). Idle periods extend the most recent window. Bucketing is used to limit the history of avg_lat by binding it to the window size. So, the window range for 1/exp (decay rate) is [1 min, 2.5 min) when windows elapse immediately. The current sample window size is exposed in the debug info to enable calculation of the window range. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-08-01blk-iolatency: fix blkg leak in timer_fnJosef Bacik1-1/+1
At this point we have a ref on the blkg, we need to drop it if we don't have a iolat. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-16blk-iolatency: truncate our current timeJosef Bacik1-0/+6
In our longer tests we noticed that some boxes would degrade to the point of uselessness. This is because we truncate the current time when saving it in our bio, but I was using the raw current time to subtract from. So once the box had been up a certain amount of time it would appear as if our IO's were taking several years to complete. Fix this by truncating the current time so it matches the issue time. Verified this worked by running with this patch for a week on our test tier. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-16blk-iolatency: don't change the latency windowJosef Bacik1-10/+0
Early versions of these patches had us waiting for seconds at a time during submission, so we had to adjust the timing window we monitored for latency. Now we don't do things like that so this is unnecessary code. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-11blk-iolatency: fix max_depth comparisonsJosef Bacik1-6/+6
max_depth used to be a u64, but I changed it to a unsigned int but didn't convert my comparisons over everywhere. Fix by using UINT_MAX everywhere instead of (u64)-1. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-10block: iolatency: avoid 64-bit divisionArnd Bergmann1-2/+1
On 32-bit architectures, dividing a 64-bit number needs to use the do_div() function or something like it to avoid a link failure: block/blk-iolatency.o: In function `iolatency_prfill_limit': blk-iolatency.c:(.text+0x8cc): undefined reference to `__aeabi_uldivmod' Using div_u64() gives us the best output and avoids the need for an explicit cast. Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-07-09block: introduce blk-iolatency io controllerJosef Bacik1-0/+930
Current IO controllers for the block layer are less than ideal for our use case. The io.max controller is great at hard limiting, but it is not work conserving. This patch introduces io.latency. You provide a latency target for your group and we monitor the io in short windows to make sure we are not exceeding those latency targets. This makes use of the rq-qos infrastructure and works much like the wbt stuff. There are a few differences from wbt - It's bio based, so the latency covers the whole block layer in addition to the actual io. - We will throttle all IO types that comes in here if we need to. - We use the mean latency over the 100ms window. This is because writes can be particularly fast, which could give us a false sense of the impact of other workloads on our protected workload. - By default there's no throttling, we set the queue_depth to INT_MAX so that we can have as many outstanding bio's as we're allowed to. Only at throttle time do we pay attention to the actual queue depth. - We backcharge cgroups for root cg issued IO and induce artificial delays in order to deal with cases like metadata only or swap heavy workloads. In testing this has worked out relatively well. Protected workloads will throttle noisy workloads down to 1 io at time if they are doing normal IO on their own, or induce up to a 1 second delay per syscall if they are doing a lot of root issued IO (metadata/swap IO). Our testing has revolved mostly around our production web servers where we have hhvm (the web server application) in a protected group and everything else in another group. We see slightly higher requests per second (RPS) on the test tier vs the control tier, and much more stable RPS across all machines in the test tier vs the control tier. Another test we run is a slow memory allocator in the unprotected group. Before this would eventually push us into swap and cause the whole box to die and not recover at all. With these patches we see slight RPS drops (usually 10-15%) before the memory consumer is properly killed and things recover within seconds. Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>