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* blk-mq: Facilitate a shared sbitmap per tagsetJohn Garry2020-09-036-7/+85
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some SCSI HBAs (such as HPSA, megaraid, mpt3sas, hisi_sas_v3 ..) support multiple reply queues with single hostwide tags. In addition, these drivers want to use interrupt assignment in pci_alloc_irq_vectors(PCI_IRQ_AFFINITY). However, as discussed in [0], CPU hotplug may cause in-flight IO completion to not be serviced when an interrupt is shutdown. That problem is solved in commit bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline"). However, to take advantage of that blk-mq feature, the HBA HW queuess are required to be mapped to that of the blk-mq hctx's; to do that, the HBA HW queues need to be exposed to the upper layer. In making that transition, the per-SCSI command request tags are no longer unique per Scsi host - they are just unique per hctx. As such, the HBA LLDD would have to generate this tag internally, which has a certain performance overhead. However another problem is that blk-mq assumes the host may accept (Scsi_host.can_queue * #hw queue) commands. In commit 6eb045e092ef ("scsi: core: avoid host-wide host_busy counter for scsi_mq"), the Scsi host busy counter was removed, which would stop the LLDD being sent more than .can_queue commands; however, it should still be ensured that the block layer does not issue more than .can_queue commands to the Scsi host. To solve this problem, introduce a shared sbitmap per blk_mq_tag_set, which may be requested at init time. New flag BLK_MQ_F_TAG_HCTX_SHARED should be set when requesting the tagset to indicate whether the shared sbitmap should be used. Even when BLK_MQ_F_TAG_HCTX_SHARED is set, a full set of tags and requests are still allocated per hctx; the reason for this is that if tags and requests were only allocated for a single hctx - like hctx0 - it may break block drivers which expect a request be associated with a specific hctx, i.e. not always hctx0. This will introduce extra memory usage. This change is based on work originally from Ming Lei in [1] and from Bart's suggestion in [2]. [0] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@nanos.tec.linutronix.de/ [1] https://lore.kernel.org/linux-block/20190531022801.10003-1-ming.lei@redhat.com/ [2] https://lore.kernel.org/linux-block/ff77beff-5fd9-9f05-12b6-826922bace1f@huawei.com/T/#m3db0a602f095cbcbff27e9c884d6b4ae826144be Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Don Brace<don.brace@microsemi.com> #SCSI resv cmds patches used Tested-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-mq: Use pointers for blk_mq_tags bitmap tagsJohn Garry2020-09-036-33/+39
| | | | | | | | | | | | Introduce pointers for the blk_mq_tags regular and reserved bitmap tags, with the goal of later being able to use a common shared tag bitmap across all HW contexts in a set. Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Don Brace<don.brace@microsemi.com> #SCSI resv cmds patches used Tested-by: Douglas Gilbert <dgilbert@interlog.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-mq: Pass flags for tag init/freeJohn Garry2020-09-035-23/+35
| | | | | | | | | | | | Pass hctx/tagset flags argument down to blk_mq_init_tags() and blk_mq_free_tags() for selective init/free. For now, make it include the alloc policy flag, which can be evaluated when needed (in blk_mq_init_tags()). Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-mq: Free tags in blk_mq_init_tags() upon errorHannes Reinecke2020-09-031-8/+10
| | | | | | | | | | | | | Since the tags are allocated in blk_mq_init_tags(), it's better practice to free in that same function upon error, rather than a callee which is to init the bitmap tags (blk_mq_init_tags()). [jpg: Split from an earlier patch with a new commit message] Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-mq: Rename blk_mq_update_tag_set_depth()Hannes Reinecke2020-09-031-4/+4
| | | | | | | | | | | | | | | The function does not set the depth, but rather transitions from shared to non-shared queues and vice versa. So rename it to blk_mq_update_tag_set_shared() to better reflect its purpose. [jpg: take out some unrelated changes in blk_mq_init_bitmap_tags()] Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-mq: Rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHAREDMing Lei2020-09-035-16/+16
| | | | | | | | | | | | | | | | BLK_MQ_F_TAG_SHARED actually means that tags is shared among request queues, all of which should belong to LUNs attached to same HBA. So rename it to make the point explicitly. [jpg: rebase a few times, add rnbd-clt.c change] Suggested-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Douglas Gilbert <dgilbert@interlog.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove revalidate_disk()Christoph Hellwig2020-09-023-21/+1
| | | | | | | | | | Remove the now unused helper. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Acked-by: Song Liu <song@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* nvdimm: simplify revalidate_disk handlingChristoph Hellwig2020-09-025-13/+7
| | | | | | | | | | | | | | | The nvdimm block driver abuse revalidate_disk in a strange way, and totally unrelated to what other drivers do. Simplify this by just calling nvdimm_revalidate_disk (which seems rather misnamed) from the probe routines, as the additional bdev size revalidation is pointless at this point, and remove the revalidate_disk methods given that it can only be triggered from add_disk, which is right before the manual calls. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* sd: open code revalidate_diskChristoph Hellwig2020-09-021-2/+4
| | | | | | | | | | Instead of calling revalidate_disk just do the work directly by calling sd_revalidate_disk, and revalidate_disk_size where needed. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* nvme: opencode revalidate_disk in nvme_validate_nsChristoph Hellwig2020-09-021-6/+10
| | | | | | | | | | | | | | | | | Keep control in the NVMe driver instead of going through an indirect call back into ->revalidate_disk. Also reorder the function a bit to be easier to follow with the additional code. And now that we have removed all callers of revalidate_disk() in the nvme code, ->revalidate_disk is only called from the open code when first opening the device. Which is of course totally pointless as we have a valid size since the initial scan, and will get an updated view through the asynchronous notifiation everytime the size changes. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: use revalidate_disk_size in set_capacity_revalidate_and_notifyChristoph Hellwig2020-09-022-6/+5
| | | | | | | | | | | Only virtio_blk and xen-blkfront set the revalidate argument to true, and both do not implement the ->revalidate_disk method. So switch to the helper that just updates the size instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: add a new revalidate_disk_size helperChristoph Hellwig2020-09-0210-35/+46
| | | | | | | | | | | | | | | | | | revalidate_disk is a relative awkward helper for driver use, as it first calls an optional driver method and then updates the block device size, while most callers either don't need the method call at all, or want to keep state between the caller and the called method. Add a revalidate_disk_size helper that just performs the update of the block device size from the gendisk one, and switch all drivers that do not implement ->revalidate_disk to use the new helper instead of revalidate_disk() Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Acked-by: Song Liu <song@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: rename bd_invalidatedChristoph Hellwig2020-09-024-11/+13
| | | | | | | | | | Replace bd_invalidate with a new BDEV_NEED_PART_SCAN flag in a bd_flags variable to better describe the condition. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: don't clear bd_invalidated in check_disk_size_changeChristoph Hellwig2020-09-021-1/+2
| | | | | | | | | | | | | | | bd_invalidated is set by check_disk_change or in add_disk to initiate a partition scan. Move it from check_disk_size_change which is called from both revalidate_disk() and bdev_disk_changed() to only the latter, as that is what is called from the block device open code (and nbd) to deal with the bd_invalidated event. revalidate_disk() on the other hand is mostly used to propagate a size update from the gendisk to the block device, which is entirely unrelated. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* Documentation/filesystems/locking.rst: remove an incorrect sentenceChristoph Hellwig2020-09-021-3/+0
| | | | | | | | | | | unlock_native_capacity is never called from check_disk_change(), and while revalidate_disk can be called from it, it can also be called from two other places at the moment. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: Remove a duplicative conditionBaolin Wang2020-09-011-4/+2
| | | | | | | | | | | Remove a duplicative condition to remove below cppcheck warnings: "warning: Redundant condition: sched_allow_merge. '!A || (A && B)' is equivalent to '!A || B' [redundantCondition]" Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: better deal with the delayed not supported case in ↵Ritika Srivastava2020-09-011-5/+22
| | | | | | | | | | | | | | | | | | blk_cloned_rq_check_limits If WRITE_ZERO/WRITE_SAME operation is not supported by the storage, blk_cloned_rq_check_limits() will return IO error which will cause device-mapper to fail the paths. Instead, if the queue limit is set to 0, return BLK_STS_NOTSUPP. BLK_STS_NOTSUPP will be ignored by device-mapper and will not fail the paths. Suggested-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Ritika Srivastava <ritika.srivastava@oracle.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: Return blk_status_t instead of errno codesRitika Srivastava2020-09-011-4/+4
| | | | | | | | | Replace returning legacy errno codes with blk_status_t in blk_cloned_rq_check_limits(). Signed-off-by: Ritika Srivastava <ritika.srivastava@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: grant IOPRIO_CLASS_RT to CAP_SYS_NICEKhazhismel Kumykov2020-09-012-1/+3
| | | | | | | | | | | CAP_SYS_ADMIN is too broad, and ionice fits into CAP_SYS_NICE's grouping. Retain CAP_SYS_ADMIN permission for backwards compatibility. Signed-off-by: Khazhismel Kumykov <khazhy@google.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Acked-by: Serge Hallyn <serge@hallyn.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: update iocost_monitor.pyTejun Heo2020-09-011-35/+19
| | | | | | | | iocost went through significant internal changes. Update iocost_monitor.py accordingly. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: add three debug stat - cost.wait, indebt and indelayTejun Heo2020-09-011-5/+72
| | | | | | | | These are really cheap to collect and can be useful in debugging iocost behavior. Add them as debug stats for now. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: restore inuse update tracepointsTejun Heo2020-09-012-3/+19
| | | | | | | Update and restore the inuse update tracepoints. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: implement vtime loss compensationTejun Heo2020-09-011-42/+90
| | | | | | | | | | | | | | When an iocg accumulates too much vtime or gets deactivated, we throw away some vtime, which lowers the overall device utilization. As the exact amount which is being thrown away is known, we can compensate by accelerating the vrate accordingly so that the extra vtime generated in the current period matches what got lost. This significantly improves work conservation when involving high weight cgroups with intermittent and bursty IO patterns. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: halve debts if device stays idleTejun Heo2020-09-011-1/+48
| | | | | | | | | | | | | | | | | A low weight iocg can amass a large amount of debt, for example, when anonymous memory gets reclaimed aggressively. If the system has a lot of memory paired with a slow IO device, the debt can span multiple seconds or more. If there are no other subsequent IO issuers, the in-debt iocg may end up blocked paying its debt while the IO device is idle. This patch implements a mechanism to protect against such pathological cases. If the device has been sufficiently idle for a substantial amount of time, the debts are halved. The criteria are on the conservative side as we want to resolve the rare extreme cases without impacting regular operation by forgiving debts too readily. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: implement delay adjustment hysteresisTejun Heo2020-09-012-56/+86
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Curently, iocost syncs the delay duration to the outstanding debt amount, which seemed enough to protect the system from anon memory hogs. However, that was mostly because the delay calcuation was using hweight_inuse which quickly converges towards zero under debt for delay duration calculation, often pusnishing debtors overly harshly for longer than deserved. The previous patch fixed the delay calcuation and now the protection against anonymous memory hogs isn't enough because the effect of delay is indirect and non-linear and a huge amount of future debt can accumulate abruptly while unthrottled. This patch implements delay hysteresis so that delay is decayed exponentially over time instead of getting cleared immediately as debt is paid off. While the overall behavior is similar to the blk-cgroup implementation used by blk-iolatency, a lot of the details are different and due to the empirical nature of the mechanism, it's challenging to adapt the mechanism for one controller without negatively impacting the other. As the delay is gradually decayed now, there's no point in running it from its own hrtimer. Periodic updates are now performed from ioc_timer_fn() and the dedicated hrtimer is removed. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: revamp debt handlingTejun Heo2020-09-011-24/+93
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Debt handling had several issues. * How much inuse a debtor carries wasn't clearly defined. inuse would be driven down over time from not issuing IOs but it'd be better to clamp it to minimum immediately once in debt. * How much can be paid off was determined by hweight_inuse. As inuse was driven down, the payment amount would fall together regardless of the debtor's active weight. This means that the debtors were punished harshly. * ioc_rqos_merge() wasn't calling blkcg_schedule_throttle() after iocg_kick_delay(). This patch revamps debt handling so that * Debt handling owns inuse for iocgs in debt and keeps them at zero. * Payment amount is determined by hweight_active. This is more deterministic and safer than hweight_inuse but still far from ideal in that it doesn't factor in possible donations from other iocgs for debt payments. This likely needs further improvements in the future. * iocg_rqos_merge() now calls blkcg_schedule_throttle() as necessary. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andy Newell <newella@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: revamp in-period donation snapbacksTejun Heo2020-09-011-37/+96
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the margin drops below the minimum on a donating iocg, donation is immediately canceled in full. There are a couple shortcomings with the current behavior. * It's abrupt. A small temporary budget deficit can lead to a wide swing in weight allocation and a large surplus. * It's open coded in the issue path but not implemented for the merge path. A series of merges at a low inuse can make the iocg incur debts and stall incorrectly. This patch reimplements in-period donation snapbacks so that * inuse adjustment and cost calculations are factored into adjust_inuse_and_calc_cost() which is called from both the issue and merge paths. * Snapbacks are more gradual. It occurs in quarter steps. * A snapback triggers if the margin goes below the low threshold and is lower than the budget at the time of the last adjustment. * For the above, __propagate_weights() stores the margin in iocg->saved_margin. Move iocg->last_inuse storing together into __propagate_weights() for consistency. * Full snapback is guaranteed when there are waiters. * With precise donation and gradual snapbacks, inuse adjustments are now a lot more effective and the value of scaling inuse on weight changes isn't clear. Removed inuse scaling from weight_update(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: revamp donation amount determinationTejun Heo2020-09-011-82/+51
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | iocost has various safety nets to combat inuse adjustment calculation inaccuracies. With Andy's method implemented in transfer_surpluses(), inuse adjustment calculations are now accurate and we can make donation amount determinations accurate too. * Stop keeping track of past usage history and using the maximum. Act on the immediate usage information. * Remove donation constraints defined by SURPLUS_* constants. Donate whatever isn't used. * Determine the donation amount so that the iocg will end up with MARGIN_TARGET_PCT budget at the end of the coming period assuming the same usage as the previous period. TARGET is set at 50% of period, which is the previous maximum. This provides smooth convergence for most repetitive IO patterns. * Apply donation logic early at 20% budget. There's no risk in doing so as the calculation is based on the delta between the current budget and the target budget at the end of the coming period. * Remove preemptive iocg activation for zero cost IOs. As donation can reach near zero now, the mere activation doesn't provide any protection anymore. In the unlikely case that this becomes a problem, the right solution is assigning appropriate costs for such IOs. This significantly improves the donation determination logic while also simplifying it. Now all donations are immediate, exact and smooth. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andy Newell <newella@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: implement Andy's method for donation weight updatesTejun Heo2020-09-011-8/+244
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | iocost implements work conservation by reducing iocg->inuse and propagating the adjustment upwards proportionally. However, while I knew the target absolute hierarchical proportion - adjusted hweight_inuse, I couldn't figure out how to determine the iocg->inuse adjustment to achieve that and approximated the adjustment by scaling iocg->inuse using the proportion of the needed hweight_inuse changes. When nested, these scalings aren't accurate even when adjusting a single node as the donating node also receives the benefit of the donated portion. When multiple nodes are donating as they often do, they can be wildly wrong. iocost employed various safety nets to combat the inaccuracies. There are ample buffers in determining how much to donate, the adjustments are conservative and gradual. While it can achieve a reasonable level of work conservation in simple scenarios, the inaccuracies can easily add up leading to significant loss of total work. This in turn makes it difficult to closely cap vrate as vrate adjustment is needed to compensate for the loss of work. The combination of inaccurate donation calculations and vrate adjustments can lead to wide fluctuations and clunky overall behaviors. Andy Newell devised a method to calculate the needed ->inuse updates to achieve the target hweight_inuse's. The method is compatible with the proportional inuse adjustment propagation which allows all hot path operations to be local to each iocg. To roughly summarize, Andy's method divides the tree into donating and non-donating parts, calculates global donation rate which is used to determine the target hweight_inuse for each node, and then derives per-level proportions. There's non-trivial amount of math involved. Please refer to the following pdfs for detailed descriptions. https://drive.google.com/file/d/1PsJwxPFtjUnwOY1QJ5AeICCcsL7BM3bo https://drive.google.com/file/d/1vONz1-fzVO7oY5DXXsLjSxEtYYQbOvsE https://drive.google.com/file/d/1WcrltBOSPN0qXVdBgnKm4mdp9FhuEFQN This patch implements Andy's method in transfer_surpluses(). This makes the donation calculations accurate per cycle and enables further improvements in other parts of the donation logic. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andy Newell <newella@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: restructure surplus donation logicTejun Heo2020-09-011-76/+103
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | The way the surplus donation logic is structured isn't great. There are two separate paths for starting/increasing donations and decreasing them making the logic harder to follow and is prone to unnecessary behavior differences. In preparation for improved donation handling, this patch restructures the code so that * All donors - new, increasing and decreasing - are funneled through the same code path. * The target donation calculation is factored into hweight_after_donation() which is called once from the same spot for all possible donors. * Actual inuse adjustment is factored into trasnfer_surpluses(). This change introduces a few behavior differences - e.g. donation amount reduction now uses the max usage of the recent three periods just like new and increasing donations, and inuse now gets adjusted upwards the same way it gets downwards. These differences are unlikely to have severely negative implications and the whole logic will be revamped soon. This patch also removes two tracepoints. The existing TPs don't quite fit the new implementation. A later patch will update and reinstate them. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: decouple vrate adjustment from surplus transfersTejun Heo2020-09-012-21/+11
| | | | | | | | | | | | | | Budget donations are inaccurate and could take multiple periods to converge. To prevent triggering vrate adjustments while surplus transfers were catching up, vrate adjustment was suppressed if donations were increasing, which was indicated by non-zero nr_surpluses. This entangling won't be necessary with the scheduled rewrite of donation mechanism which will make it precise and immediate. Let's decouple the two in preparation. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: replace iocg->has_surplus with ->surplus_listTejun Heo2020-09-011-8/+11
| | | | | | | | | | Instead of marking iocgs with surplus with a flag and filtering for them while walking all active iocgs, build a surpluses list. This doesn't make much difference now but will help implementing improved donation logic which will iterate iocgs with surplus multiple times. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: calculate iocg->usages[] from iocg->local_stat.usage_usTejun Heo2020-09-012-32/+47
| | | | | | | | | | | | | | | | Currently, iocg->usages[] which are used to guide inuse adjustments are calculated from vtime deltas. This, however, assumes that the hierarchical inuse weight at the time of calculation held for the entire period, which often isn't true and can lead to significant errors. Now that we have absolute usage information collected, we can derive iocg->usages[] from iocg->local_stat.usage_us so that inuse adjustment decisions are made based on actual absolute usage. The calculated usage is clamped between 1 and WEIGHT_ONE and WEIGHT_ONE is also used to signal saturation regardless of the current hierarchical inuse weight. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: add absolute usage statTejun Heo2020-09-011-6/+149
| | | | | | | | | | | | | | | | | | | Currently, iocost doesn't collect or expose any statistics punting off all monitoring duties to drgn based iocost_monitor.py. While it works for some scenarios, there are some usability and data availability challenges. For example, accurate per-cgroup usage information can't be tracked by vtime progression at all and the number available in iocg->usages[] are really short-term snapshots used for control heuristics with possibly significant errors. This patch implements per-cgroup absolute usage stat counter and exposes it through io.stat along with the current vrate. Usage stat collection and flushing employ the same method as cgroup rstat on the active iocg's and the only hot path overhead is preemption toggling and adding to a percpu counter. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: grab ioc->lock for debt handlingTejun Heo2020-09-011-19/+73
| | | | | | | | | | | | | | | | | | | | Currently, debt handling requires only iocg->waitq.lock. In the future, we want to adjust and propagate inuse changes depending on debt status. Let's grab ioc->lock in debt handling paths in preparation. * Because ioc->lock nests outside iocg->waitq.lock, the decision to grab ioc->lock needs to be made before entering the critical sections. * Add and use iocg_[un]lock() which handles the conditional double locking. * Add @pay_debt to iocg_kick_waitq() so that debt payment happens only when the caller grabbed both locks. This patch is prepatory and the comments contain references to future changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: streamline vtime margin and timer slack handlingTejun Heo2020-09-011-29/+38
| | | | | | | | | | | | | | | | | | | | | | | | | | | The margin handling was pretty inconsistent. * ioc->margin_us and ioc->inuse_margin_vtime were used as vtime margin thresholds. However, the two are in different units with the former requiring conversion to vtime on use. * iocg_kick_waitq() was using a quarter of WAITQ_TIMER_MARGIN_PCT of period_us as the timer slack - ~1.2%. While iocg_kick_delay() was using a quarter of ioc->margin_us - ~12.5%. There aren't strong reasons to use different values for the two. This patch cleans up margin and timer slack handling: * vtime margins are now recorded in ioc->margins.{min, max} on period duration changes and used consistently. * Timer slack is now 1% of period_us and recorded in ioc->timer_slack_ns and used consistently for iocg_kick_waitq() and iocg_kick_delay(). The only functional change is shortening of timer slack. No meaningful visible change is expected. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: make ioc_now->now and ioc->period_at 64bitTejun Heo2020-09-011-2/+2
| | | | | | | | | They are in microseconds and wrap in around 1.2 hours with u32. While unlikely, confusions from wraparounds are still possible. We aren't saving anything meaningful by keeping these u32. Let's make them u64. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: use WEIGHT_ONE based fixed point number for weightsTejun Heo2020-09-011-12/+13
| | | | | | | | | | | To improve weight donations, we want to able to scale inuse with a greater accuracy and down below 1. Let's make non-hierarchical weights to use WEIGHT_ONE based fixed point numbers too like hierarchical ones. This doesn't cause any behavior changes yet. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: s/HWEIGHT_WHOLE/WEIGHT_ONE/gTejun Heo2020-09-011-10/+10
| | | | | | | | | | We're gonna use HWEIGHT_WHOLE for regular weights too. Let's rename it to WEIGHT_ONE. Pure rename. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: make iocg_kick_waitq() call iocg_kick_delay() after paying debtTejun Heo2020-09-011-1/+2
| | | | | | | | | | | | | iocg_kick_waitq() is the function which pays debt and iocg_kick_delay() updates the actual delay status accordingly. If iocg_kick_delay() is not called after iocg_kick_delay() updated debt, unnecessarily large delays can be applied temporarily. Let's make sure such conditions don't occur by making iocg_kick_waitq() always call iocg_kick_delay() after paying debt. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: move iocg_kick_delay() above iocg_kick_waitq()Tejun Heo2020-09-011-60/+60
| | | | | | | | We'll make iocg_kick_waitq() call iocg_kick_delay(). Reorder them in preparation. This is pure code reorganization. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: clamp inuse and skip noops in __propagate_weights()Tejun Heo2020-09-011-1/+4
| | | | | | | | | | | | | __propagate_weights() currently expects the callers to clamp inuse within [1, active], which is needlessly fragile. The inuse adjustment logic is going to be revamped, in preparation, let's make __propagate_weights() clamp inuse on entry. Also, make it avoid weight updates altogether if neither active or inuse is changed. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: rename propagate_active_weights() to propagate_weights()Tejun Heo2020-09-011-20/+20
| | | | | | | | | | | | It already propagates two weights - active and inuse - and there will be another soon. Let's drop the confusing misnomers. Rename [__]propagate_active_weights() to [__]propagate_weights() and commit_active_weights() to commit_weights(). This is pure rename. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* blk-iocost: use local[64]_t for percpu statTejun Heo2020-09-011-10/+27
| | | | | | | | | blk-iocost has been reading percpu stat counters from remote cpus which on some archs can lead to torn reads in really rare occassions. Use local[64]_t for those counters. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove the unused q argument to part_in_flight and part_in_flight_rwChristoph Hellwig2020-09-011-7/+5
| | | | | Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove the disk argument to delete_partitionChristoph Hellwig2020-09-013-6/+7
| | | | | | | We can trivially derive the gendisk from the hd_struct. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: cleanup __alloc_disk_nodeChristoph Hellwig2020-09-011-35/+38
| | | | | | | Use early returns and goto-based unwinding to simplify the flow a bit. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: move the devcgroup_inode_permission call to blkdev_getChristoph Hellwig2020-09-011-19/+17
| | | | | | | | devcgroup_inode_permission is never called for the recusive case, so move it out into blkdev_get. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove an outdated comment on the bd_dev fieldChristoph Hellwig2020-09-011-1/+1
| | | | | | | kdev_t is long gone, so we don't need to comment a field isn't one.. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove the discard_alignment field from struct hd_structChristoph Hellwig2020-09-013-6/+6
| | | | | | | | The alignment offset is only used in slow path callers, so just calculate it on the fly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-28 10:53:37 +0000