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2023-01-15block, bfq: switch 'bfqg->ref' to use atomic refcount apisYu Kuai1-1/+1
The updating of 'bfqg->ref' should be protected by 'bfqd->lock', however, during code review, we found that bfq_pd_free() update 'bfqg->ref' without holding the lock, which is problematic: 1) bfq_pd_free() triggered by removing cgroup is called asynchronously; 2) bfqq will grab bfqg reference, and exit bfqq will drop the reference, which can concurrent with 1). Unfortunately, 'bfqd->lock' can't be held here because 'bfqd' might already be freed in bfq_pd_free(). Fix the problem by using atomic refcount apis. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20230103084755.1256479-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-12-15block, bfq: only do counting of pending-request for BFQ_GROUP_IOSCHEDYuwei Guan1-0/+4
The 'bfqd->num_groups_with_pending_reqs' is used when CONFIG_BFQ_GROUP_IOSCHED is enabled, so let the variables and processes take effect when CONFIG_BFQ_GROUP_IOSCHED is enabled. Cc: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Yuwei Guan <Yuwei.Guan@zeekrlife.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20221110112622.389332-1-Yuwei.Guan@zeekrlife.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: don't declare 'bfqd' as type 'void *' in bfq_groupYu Kuai1-1/+1
Prevent unnecessary format conversion for bfqg->bfqd in multiple places. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@unimore.it> Link: https://lore.kernel.org/r/20221102022542.3621219-6-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: cleanup __bfq_weights_tree_remove()Yu Kuai1-1/+0
It's the same with bfq_weights_tree_remove() now. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220916071942.214222-7-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: cleanup bfq_weights_tree add/remove apisYu Kuai1-7/+3
The 'bfq_data' and 'rb_root_cached' can both be accessed through 'bfq_queue', thus only pass 'bfq_queue' as parameter. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220916071942.214222-6-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: refactor the counting of 'num_groups_with_pending_reqs'Yu Kuai1-9/+9
Currently, bfq can't handle sync io concurrently as long as they are not issued from root group. This is because 'bfqd->num_groups_with_pending_reqs > 0' is always true in bfq_asymmetric_scenario(). The way that bfqg is counted into 'num_groups_with_pending_reqs': Before this patch: 1) root group will never be counted. 2) Count if bfqg or it's child bfqgs have pending requests. 3) Don't count if bfqg and it's child bfqgs complete all the requests. After this patch: 1) root group is counted. 2) Count if bfqg have pending requests. 3) Don't count if bfqg complete all the requests. With this change, the occasion that only one group is activated can be detected, and next patch will support concurrent sync io in the occasion. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220916071942.214222-4-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: record how many queues have pending requestsYu Kuai1-0/+1
Prepare to refactor the counting of 'num_groups_with_pending_reqs'. Add a counter in bfq_group, update it while tracking if bfqq have pending requests and when bfq_bfqq_move() is called. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220916071942.214222-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-11-01block, bfq: support to track if bfqq has pending requestsYu Kuai1-0/+2
If entity belongs to bfqq, then entity->in_groups_with_pending_reqs is not used currently. This patch use it to track if bfqq has pending requests through callers of weights_tree insertion and removal. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220916071942.214222-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-20block, bfq: remove unused variable for bfq_queueYuwei Guan1-4/+0
it defined in d0edc2473be9d, but there's nowhere to use it, so remove it. Signed-off-by: Yuwei Guan <Yuwei.Guan@zeekrlife.com> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20221018030139.159-1-Yuwei.Guan@zeekrlife.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-08-22block, bfq: remove useless parameter for bfq_add/del_bfqq_busy()Yu Kuai1-3/+2
'bfqd' can be accessed through 'bfqq->bfqd', there is no need to pass it as a parameter separately. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220816015631.1323948-4-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-08-22block, bfq: remove unused functionsYu Kuai1-5/+8
While doing code coverage testing(CONFIG_BFQ_CGROUP_DEBUG is disabled), we found that some functions doesn't have caller, thus remove them. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220816015631.1323948-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-07-14block/bfq: Use the new blk_opf_t typeBart Van Assche1-4/+4
Use the new blk_opf_t type for arguments and variables that represent request flags or a bitwise combination of a request operation and request flags. Rename those variables from 'op' into 'opf'. This patch does not change any functionality. Cc: Jan Kara <jack@suse.cz> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20220714180729.1065367-8-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-05-19bfq: Relax waker detection for shared queuesJan Kara1-0/+1
Currently we look for waker only if current queue has no requests. This makes sense for bfq queues with a single process however for shared queues when there is a larger number of processes the condition that queue has no requests is difficult to meet because often at least one process has some request in flight although all the others are waiting for the waker to do the work and this harms throughput. Relax the "no queued request for bfq queue" condition to "the current task has no queued requests yet". For this, we also need to start tracking number of requests in flight for each task. This patch (together with the following one) restores the performance for dbench with 128 clients that regressed with commit c65e6fd460b4 ("bfq: Do not let waker requests skip proper accounting") because this commit makes requests of wakers properly enter BFQ queues and thus these queues become ineligible for the old waker detection logic. Dbench results: Vanilla 5.18-rc3 5.18-rc3 + revert 5.18-rc3 patched Mean 1237.36 ( 0.00%) 950.16 * 23.21%* 988.35 * 20.12%* Numbers are time to complete workload so lower is better. Fixes: c65e6fd460b4 ("bfq: Do not let waker requests skip proper accounting") Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220519105235.31397-1-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-05-02blktrace: cleanup the __trace_note_message interfaceChristoph Hellwig1-2/+2
Pass the cgroup_subsys_state instead of a the blkg so that blktrace doesn't need to poke into blk-cgroup internals, and give the name a blk prefix as the current name is way too generic for a public interface. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20220420042723.1010598-9-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-04-17bfq: Get rid of __bio_blkcg() usageJan Kara1-2/+1
BFQ usage of __bio_blkcg() is a relict from the past. Furthermore if bio would not be associated with any blkcg, the usage of __bio_blkcg() in BFQ is prone to races with the task being migrated between cgroups as __bio_blkcg() calls at different places could return different blkcgs. Convert BFQ to the new situation where bio->bi_blkg is initialized in bio_set_dev() and thus practically always valid. This allows us to save blkcg_gq lookup and noticeably simplify the code. CC: stable@vger.kernel.org Fixes: 0fe061b9f03c ("blkcg: fix ref count issue with bio_blkcg() using task_css") Tested-by: "yukuai (C)" <yukuai3@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220401102752.8599-8-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-04-17bfq: Track whether bfq_group is still onlineJan Kara1-0/+2
Track whether bfq_group is still online. We cannot rely on blkcg_gq->online because that gets cleared only after all policies are offlined and we need something that gets updated already under bfqd->lock when we are cleaning up our bfq_group to be able to guarantee that when we see online bfq_group, it will stay online while we are holding bfqd->lock lock. CC: stable@vger.kernel.org Tested-by: "yukuai (C)" <yukuai3@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220401102752.8599-7-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-04-17bfq: Split shared queues on move between cgroupsJan Kara1-0/+1
When bfqq is shared by multiple processes it can happen that one of the processes gets moved to a different cgroup (or just starts submitting IO for different cgroup). In case that happens we need to split the merged bfqq as otherwise we will have IO for multiple cgroups in one bfqq and we will just account IO time to wrong entities etc. Similarly if the bfqq is scheduled to merge with another bfqq but the merge didn't happen yet, cancel the merge as it need not be valid anymore. CC: stable@vger.kernel.org Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support") Tested-by: "yukuai (C)" <yukuai3@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220401102752.8599-3-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-18block, bfq: cleanup bfq_bfqq_to_bfqg()Yu Kuai1-1/+0
Use bfq_group() instead, which do the same thing. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20220129015924.3958918-2-yukuai3@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-11block: partition include/linux/blk-cgroup.hMing Lei1-1/+0
Partition include/linux/blk-cgroup.h into two parts: one is public part, the other is block layer private part. Suggested by Christoph Hellwig. Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220211101149.2368042-4-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29bfq: Provide helper to generate bfqq nameJan Kara1-14/+13
Instead of having helper formating bfqq pid, provide a helper to generate full bfqq name as used in the traces. It saves some code duplication and will save more in the coming tracepoints. Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20211125133645.27483-6-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29bfq: Limit waker detection in timeJan Kara1-0/+2
Currently, when process A starts issuing requests shortly after process B has completed some IO three times in a row, we decide that B is a "waker" of A meaning that completing IO of B is needed for A to make progress and generally stop separating A's and B's IO much. This logic is useful to avoid unnecessary idling and thus throughput loss for cases where workload needs to switch e.g. between the process and the journaling thread doing IO. However the detection heuristic tends to frequently give false positives when A and B are fighting IO bandwidth and other processes aren't doing much IO as we are basically deemed to eventually accumulate three occurences of a situation where one process starts issuing requests after the other has completed some IO. To reduce these false positives, cancel the waker detection also if we didn't accumulate three detected wakeups within given timeout. The rationale is that if wakeups are really rare, the pointless idling doesn't hurt throughput that much anyway. This significantly reduces false waker detection for workload like: [global] directory=/mnt/repro/ rw=write size=8g time_based runtime=30 ramp_time=10 blocksize=1m direct=0 ioengine=sync [slowwriter] numjobs=1 fsync=200 [fastwriter] numjobs=1 fsync=200 Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20211125133645.27483-5-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29bfq: Store full bitmap depth in bfq_dataJan Kara1-0/+1
Store bitmap depth shift inside bfq_data so that we can use it in bfq_limit_depth() for proportioning when limiting number of available request tags for a cgroup. Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20211125133645.27483-3-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-11-29bfq: Track number of allocated requests in bfq_entityJan Kara1-2/+3
When we want to limit number of requests used by each bfqq and also cgroup, we need to track also number of requests used by each cgroup. So track number of allocated requests for each bfq_entity. Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20211125133645.27483-2-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-25block, bfq: cleanup the repeated declarationShaokun Zhang1-2/+0
Function 'bfq_entity_to_bfqq' is declared twice, so remove the repeated declaration and blank line. Cc: Paolo Valente <paolo.valente@linaro.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com> Link: https://lore.kernel.org/r/1629872391-46399-1-git-send-email-zhangshaokun@hisilicon.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-18block: Introduce IOPRIO_NR_LEVELSDamien Le Moal1-2/+2
The BFQ scheduler and ioprio_check_cap() both assume that the RT priority class (IOPRIO_CLASS_RT) can have up to 8 different priority levels, similarly to the BE class (IOPRIO_CLASS_iBE). This is controlled using the IOPRIO_BE_NR macro , which is badly named as the number of levels also applies to the RT class. Introduce the class independent IOPRIO_NR_LEVELS macro, defined to 8, to make things clear. Keep the old IOPRIO_BE_NR macro definition as an alias for IOPRIO_NR_LEVELS. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Link: https://lore.kernel.org/r/20210811033702.368488-6-damien.lemoal@wdc.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-25block, bfq: merge bursts of newly-created queuesPaolo Valente1-0/+15
Many throughput-sensitive workloads are made of several parallel I/O flows, with all flows generated by the same application, or more generically by the same task (e.g., system boot). The most counterproductive action with these workloads is plugging I/O dispatch when one of the bfq_queues associated with these flows remains temporarily empty. To avoid this plugging, BFQ has been using a burst-handling mechanism for years now. This mechanism has proven effective for throughput, and not detrimental for service guarantees. This commit pushes this mechanism a little bit further, basing on the following two facts. First, all the I/O flows of a the same application or task contribute to the execution/completion of that common application or task. So the performance figures that matter are total throughput of the flows and task-wide I/O latency. In particular, these flows do not need to be protected from each other, in terms of individual bandwidth or latency. Second, the above fact holds regardless of the number of flows. Putting these two facts together, this commits merges stably the bfq_queues associated with these I/O flows, i.e., with the processes that generate these IO/ flows, regardless of how many the involved processes are. To decide whether a set of bfq_queues is actually associated with the I/O flows of a common application or task, and to merge these queues stably, this commit operates as follows: given a bfq_queue, say Q2, currently being created, and the last bfq_queue, say Q1, created before Q2, Q2 is merged stably with Q1 if - very little time has elapsed since when Q1 was created - Q2 has the same ioprio as Q1 - Q2 belongs to the same group as Q1 Merging bfq_queues also reduces scheduling overhead. A fio test with ten random readers on /dev/nullb shows a throughput boost of 40%, with a quadcore. Since BFQ's execution time amounts to ~50% of the total per-request processing time, the above throughput boost implies that BFQ's overhead is reduced by more than 50%. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Link: https://lore.kernel.org/r/20210304174627.161-7-paolo.valente@linaro.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-25block, bfq: make waker-queue detection more robustPaolo Valente1-2/+5
In the presence of many parallel I/O flows, the detection of waker bfq_queues suffers from false positives. This commits addresses this issue by making the filtering of actual wakers more selective. In more detail, a candidate waker must be found to meet waker requirements three times before being promoted to actual waker. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-25block, bfq: save also injection state on queue mergingPaolo Valente1-0/+5
To prevent injection information from being lost on bfq_queue merging, also the amount of service that a bfq_queue receives must be saved and restored when the bfq_queue is merged and split, respectively. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-25block, bfq: save also weight-raised service on queue mergingPaolo Valente1-0/+1
To prevent weight-raising information from being lost on bfq_queue merging, also the amount of service that a bfq_queue receives must be saved and restored when the bfq_queue is merged and split, respectively. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-25block, bfq: replace mechanism for evaluating I/O intensityPaolo Valente1-8/+8
Some BFQ mechanisms make their decisions on a bfq_queue basing also on whether the bfq_queue is I/O bound. In this respect, the current logic for evaluating whether a bfq_queue is I/O bound is rather rough. This commits replaces this logic with a more effective one. The new logic measures the percentage of time during which a bfq_queue is active, and marks the bfq_queue as I/O bound if the latter if this percentage is above a fixed threshold. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-18bfq: fix blkio cgroup leakage v4Dmitry Monakhov1-1/+0
Changes from v1: - update commit description with proper ref-accounting justification commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") introduce leak forbfq_group and blkcg_gq objects because of get/put imbalance. In fact whole idea of original commit is wrong because bfq_group entity can not dissapear under us because it is referenced by child bfq_queue's entities from here: -> bfq_init_entity() ->bfqg_and_blkg_get(bfqg); ->entity->parent = bfqg->my_entity -> bfq_put_queue(bfqq) FINAL_PUT ->bfqg_and_blkg_put(bfqq_group(bfqq)) ->kmem_cache_free(bfq_pool, bfqq); So parent entity can not disappear while child entity is in tree, and child entities already has proper protection. This patch revert commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") bfq_group leak trace caused by bad commit: -> blkg_alloc -> bfq_pq_alloc -> bfqg_get (+1) ->bfq_activate_bfqq ->bfq_activate_requeue_entity -> __bfq_activate_entity ->bfq_get_entity ->bfqg_and_blkg_get (+1) <==== : Note1 ->bfq_del_bfqq_busy ->bfq_deactivate_entity+0x53/0xc0 [bfq] ->__bfq_deactivate_entity+0x1b8/0x210 [bfq] -> bfq_forget_entity(is_in_service = true) entity->on_st_or_in_serv = false <=== :Note2 if (is_in_service) return; ==> do not touch reference -> blkcg_css_offline -> blkcg_destroy_blkgs -> blkg_destroy -> bfq_pd_offline -> __bfq_deactivate_entity if (!entity->on_st_or_in_serv) /* true, because (Note2) return false; -> bfq_pd_free -> bfqg_put() (-1, byt bfqg->ref == 2) because of (Note2) So bfq_group and blkcg_gq will leak forever, see test-case below. ##TESTCASE_BEGIN: #!/bin/bash max_iters=${1:-100} #prep cgroup mounts mount -t tmpfs cgroup_root /sys/fs/cgroup mkdir /sys/fs/cgroup/blkio mount -t cgroup -o blkio none /sys/fs/cgroup/blkio # Prepare blkdev grep blkio /proc/cgroups truncate -s 1M img losetup /dev/loop0 img echo bfq > /sys/block/loop0/queue/scheduler grep blkio /proc/cgroups for ((i=0;i<max_iters;i++)) do mkdir -p /sys/fs/cgroup/blkio/a echo 0 > /sys/fs/cgroup/blkio/a/cgroup.procs dd if=/dev/loop0 bs=4k count=1 of=/dev/null iflag=direct 2> /dev/null echo 0 > /sys/fs/cgroup/blkio/cgroup.procs rmdir /sys/fs/cgroup/blkio/a grep blkio /proc/cgroups done ##TESTCASE_END: Fixes: db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-03-21block, bfq: turn put_queue into release_process_ref in __bfq_bic_change_cgroupPaolo Valente1-0/+1
A bfq_put_queue() may be invoked in __bfq_bic_change_cgroup(). The goal of this put is to release a process reference to a bfq_queue. But process-reference releases may trigger also some extra operation, and, to this goal, are handled through bfq_release_process_ref(). So, turn the invocation of bfq_put_queue() into an invocation of bfq_release_process_ref(). Tested-by: cki-project@redhat.com Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-02-03block, bfq: get a ref to a group when adding it to a service treePaolo Valente1-0/+1
BFQ schedules generic entities, which may represent either bfq_queues or groups of bfq_queues. When an entity is inserted into a service tree, a reference must be taken, to make sure that the entity does not disappear while still referred in the tree. Unfortunately, such a reference is mistakenly taken only if the entity represents a bfq_queue. This commit takes a reference also in case the entity represents a group. Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by: Chris Evich <cevich@redhat.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-02-03block, bfq: remove ifdefs from around gets/puts of bfq groupsPaolo Valente1-0/+1
ifdefs around gets and puts of bfq groups reduce readability, remove them. Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Reported-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-02-03block, bfq: extend incomplete name of field on_stPaolo Valente1-1/+1
The flag on_st in the bfq_entity data structure is true if the entity is on a service tree or is in service. Yet the name of the field, confusingly, does not mention the second, very important case. Extend the name to mention the second case too. Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-20block,bfq: Skip tracing hooks if possibleDmitry Monakhov1-0/+4
In most cases blk_tracing is not active, but bfq_log_bfqq macro generate pid_str unconditionally, which result in significant overhead. ## Test modprobe null_blk echo bfq > /sys/block/nullb0/queue/scheduler fio --name=t --ioengine=libaio --direct=1 --filename=/dev/nullb0 \ --runtime=30 --time_based=1 --rw=write --iodepth=128 --bs=4k # Results | | baseline | w/ patch | gain | | iops | 113.19K | 126.42K | +11% | Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-07blk-cgroup: separate out blkg_rwstat under CONFIG_BLK_CGROUP_RWSTATTejun Heo1-0/+2
blkg_rwstat is now only used by bfq-iosched and blk-throtl when on cgroup1. Let's move it into its own files and gate it behind a config option. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-07bfq-iosched: stop using blkg->stat_bytes and ->stat_iosTejun Heo1-0/+4
When used on cgroup1, bfq uses the blkg->stat_bytes and ->stat_ios from blk-cgroup core to populate six stat knobs. blk-cgroup core is moving away from blkg_rwstat to improve scalability and won't be able to support this usage. It isn't like the sharing gains all that much. Let's break it out to dedicated rwstat counters which are updated when on cgroup1. This makes use of bfqg_*rwstat*() helpers outside of CONFIG_BFQ_CGROUP_DEBUG. Move them out. v2: Compile fix when !CONFIG_BFQ_CGROUP_DEBUG. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-06bfq: Add per-device weightFam Zheng1-0/+3
This adds to BFQ the missing per-device weight interfaces: blkio.bfq.weight_device on legacy and io.bfq.weight on unified. The implementation pretty closely resembles what we had in CFQ and the parsing code is basically reused. Tests ===== Using two cgroups and three block devices, having weights setup as: Cgroup test1 test2 ============================================ default 100 500 sda 500 100 sdb default default sdc 200 200 cgroup v1 runs -------------- sda.test1.out: READ: bw=913MiB/s sda.test2.out: READ: bw=183MiB/s sdb.test1.out: READ: bw=213MiB/s sdb.test2.out: READ: bw=1054MiB/s sdc.test1.out: READ: bw=650MiB/s sdc.test2.out: READ: bw=650MiB/s cgroup v2 runs -------------- sda.test1.out: READ: bw=915MiB/s sda.test2.out: READ: bw=184MiB/s sdb.test1.out: READ: bw=216MiB/s sdb.test2.out: READ: bw=1069MiB/s sdc.test1.out: READ: bw=621MiB/s sdc.test2.out: READ: bw=622MiB/s Signed-off-by: Fam Zheng <zhengfeiran@bytedance.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-25block, bfq: detect wakers and unconditionally inject their I/OPaolo Valente1-1/+24
A bfq_queue Q may happen to be synchronized with another bfq_queue Q2, i.e., the I/O of Q2 may need to be completed for Q to receive new I/O. We call Q2 "waker queue". If I/O plugging is being performed for Q, and Q is not receiving any more I/O because of the above synchronization, then, thanks to BFQ's injection mechanism, the waker queue is likely to get served before the I/O-plugging timeout fires. Unfortunately, this fact may not be sufficient to guarantee a high throughput during the I/O plugging, because the inject limit for Q may be too low to guarantee a lot of injected I/O. In addition, the duration of the plugging, i.e., the time before Q finally receives new I/O, may not be minimized, because the waker queue may happen to be served only after other queues. To address these issues, this commit introduces the explicit detection of the waker queue, and the unconditional injection of a pending I/O request of the waker queue on each invocation of bfq_dispatch_request(). One may be concerned that this systematic injection of I/O from the waker queue delays the service of Q's I/O. Fortunately, it doesn't. On the contrary, next Q's I/O is brought forward dramatically, for it is not blocked for milliseconds. Reported-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu> Tested-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-20block: rename CONFIG_DEBUG_BLK_CGROUP to CONFIG_BFQ_CGROUP_DEBUGChristoph Hellwig1-2/+2
This option is entirely bfq specific, give it an appropinquate name. Also make it depend on CONFIG_BFQ_GROUP_IOSCHED in Kconfig, as all the functionality already does so anyway. Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-20blk-cgroup: move struct blkg_stat to bfqChristoph Hellwig1-7/+12
This structure and assorted infrastructure is only used by the bfq I/O scheduler. Move it there instead of bloating the common code. Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-30block: switch all files cleared marked as GPLv2 or later to SPDX tagsChristoph Hellwig1-10/+1
All these files have some form of the usual GPLv2 or later boilerplate. Switch them to use SPDX tags instead. Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-22Merge tag 'v5.1-rc6' into for-5.2/blockJens Axboe1-1/+1
Pull in v5.1-rc6 to resolve two conflicts. One is in BFQ, in just a comment, and is trivial. The other one is a conflict due to a later fix in the bio multi-page work, and needs a bit more care. * tag 'v5.1-rc6': (770 commits) Linux 5.1-rc6 block: make sure that bvec length can't be overflow block: kill all_q_node in request_queue x86/cpu/intel: Lower the "ENERGY_PERF_BIAS: Set to normal" message's log priority coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping mm/kmemleak.c: fix unused-function warning init: initialize jump labels before command line option parsing kernel/watchdog_hld.c: hard lockup message should end with a newline kcov: improve CONFIG_ARCH_HAS_KCOV help text mm: fix inactive list balancing between NUMA nodes and cgroups mm/hotplug: treat CMA pages as unmovable proc: fixup proc-pid-vm test proc: fix map_files test on F29 mm/vmstat.c: fix /proc/vmstat format for CONFIG_DEBUG_TLBFLUSH=y CONFIG_SMP=n mm/memory_hotplug: do not unlock after failing to take the device_hotplug_lock mm: swapoff: shmem_unuse() stop eviction without igrab() mm: swapoff: take notice of completion sooner mm: swapoff: remove too limiting SWAP_UNUSE_MAX_TRIES mm: swapoff: shmem_find_swap_entries() filter out other types slab: store tagged freelist for off-slab slabmgmt ... Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-10block, bfq: fix use after free in bfq_bfqq_expirePaolo Valente1-1/+1
The function bfq_bfqq_expire() invokes the function __bfq_bfqq_expire(), and the latter may free the in-service bfq-queue. If this happens, then no other instruction of bfq_bfqq_expire() must be executed, or a use-after-free will occur. Basing on the assumption that __bfq_bfqq_expire() invokes bfq_put_queue() on the in-service bfq-queue exactly once, the queue is assumed to be freed if its refcounter is equal to one right before invoking __bfq_bfqq_expire(). But, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") this assumption is false. __bfq_bfqq_expire() may also invoke bfq_weights_tree_remove() and, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree"), also the latter function may invoke bfq_put_queue(). So __bfq_bfqq_expire() may invoke bfq_put_queue() twice, and this is the actual case where the in-service queue may happen to be freed. To address this issue, this commit moves the check on the refcounter of the queue right around the last bfq_put_queue() that may be invoked on the queue. Fixes: 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") Reported-by: Dmitrii Tcvetkov <demfloro@demfloro.ru> Reported-by: Douglas Anderson <dianders@chromium.org> Tested-by: Dmitrii Tcvetkov <demfloro@demfloro.ru> Tested-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-08block, bfq: fix some typos in commentsAngelo Ruocco1-2/+2
Some of the comments in the bfq files had typos. This patch fixes them. Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-01block, bfq: save & resume weight on a queue merge/splitFrancesco Pollicino1-0/+9
bfq saves the state of a queue each time a merge occurs, to be able to resume such a state when the queue is associated again with its original process, on a split. Unfortunately bfq does not save & restore also the weight of the queue. If the weight is not correctly resumed when the queue is recycled, then the weight of the recycled queue could differ from the weight of the original queue. This commit adds the missing save & resume of the weight. Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Francesco Pollicino <fra.fra.800@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-01block, bfq: print SHARED instead of pid for shared queues in logsFrancesco Pollicino1-4/+19
The function "bfq_log_bfqq" prints the pid of the process associated with the queue passed as input. Unfortunately, if the queue is shared, then more than one process is associated with the queue. The pid that gets printed in this case is the pid of one of the associated processes. Which process gets printed depends on the exact sequence of merge events the queue underwent. So printing such a pid is rather useless and above all is often rather confusing because it reports a random pid between those of the associated processes. This commit addresses this issue by printing SHARED instead of a pid if the queue is shared. Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Francesco Pollicino <fra.fra.800@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-01block, bfq: do not merge queues on flash storage with queueingPaolo Valente1-0/+3
To boost throughput with a set of processes doing interleaved I/O (i.e., a set of processes whose individual I/O is random, but whose merged cumulative I/O is sequential), BFQ merges the queues associated with these processes, i.e., redirects the I/O of these processes into a common, shared queue. In the shared queue, I/O requests are ordered by their position on the medium, thus sequential I/O gets dispatched to the device when the shared queue is served. Queue merging costs execution time, because, to detect which queues to merge, BFQ must maintain a list of the head I/O requests of active queues, ordered by request positions. Measurements showed that this costs about 10% of BFQ's total per-request processing time. Request processing time becomes more and more critical as the speed of the underlying storage device grows. Yet, fortunately, queue merging is basically useless on the very devices that are so fast to make request processing time critical. To reach a high throughput, these devices must have many requests queued at the same time. But, in this configuration, the internal scheduling algorithms of these devices do also the job of queue merging: they reorder requests so as to obtain as much as possible a sequential I/O pattern. As a consequence, with processes doing interleaved I/O, the throughput reached by one such device is likely to be the same, with and without queue merging. In view of this fact, this commit disables queue merging, and all related housekeeping, for non-rotational devices with internal queueing. The total, single-lock-protected, per-request processing time of BFQ drops to, e.g., 1.9 us on an Intel Core i7-2760QM@2.40GHz (time measured with simple code instrumentation, and using the throughput-sync.sh script of the S suite [1], in performance-profiling mode). To put this result into context, the total, single-lock-protected, per-request execution time of the lightest I/O scheduler available in blk-mq, mq-deadline, is 0.7 us (mq-deadline is ~800 LOC, against ~10500 LOC for BFQ). Disabling merging provides a further, remarkable benefit in terms of throughput. Merging tends to make many workloads artificially more uneven, mainly because of shared queues remaining non empty for incomparably more time than normal queues. So, if, e.g., one of the queues in a set of merged queues has a higher weight than a normal queue, then the shared queue may inherit such a high weight and, by staying almost always active, may force BFQ to perform I/O plugging most of the time. This evidently makes it harder for BFQ to let the device reach a high throughput. As a practical example of this problem, and of the benefits of this commit, we measured again the throughput in the nasty scenario considered in previous commit messages: dbench test (in the Phoronix suite), with 6 clients, on a filesystem with journaling, and with the journaling daemon enjoying a higher weight than normal processes. With this commit, the throughput grows from ~150 MB/s to ~200 MB/s on a PLEXTOR PX-256M5 SSD. This is the same peak throughput reached by any of the other I/O schedulers. As such, this is also likely to be the maximum possible throughput reachable with this workload on this device, because I/O is mostly random, and the other schedulers basically just pass I/O requests to the drive as fast as possible. [1] https://github.com/Algodev-github/S Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by: Francesco Pollicino <fra.fra.800@gmail.com> Signed-off-by: Alessio Masola <alessio.masola@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-01block, bfq: tune service injection basing on request service timesPaolo Valente1-23/+28
The processes associated with a bfq_queue, say Q, may happen to generate their cumulative I/O at a lower rate than the rate at which the device could serve the same I/O. This is rather probable, e.g., if only one process is associated with Q and the device is an SSD. It results in Q becoming often empty while in service. If BFQ is not allowed to switch to another queue when Q becomes empty, then, during the service of Q, there will be frequent "service holes", i.e., time intervals during which Q gets empty and the device can only consume the I/O already queued in its hardware queues. This easily causes considerable losses of throughput. To counter this problem, BFQ implements a request injection mechanism, which tries to fill the above service holes with I/O requests taken from other bfq_queues. The hard part in this mechanism is finding the right amount of I/O to inject, so as to both boost throughput and not break Q's bandwidth and latency guarantees. To this goal, the current version of this mechanism measures the bandwidth enjoyed by Q while it is being served, and tries to inject the maximum possible amount of extra service that does not cause Q's bandwidth to decrease too much. This solution has an important shortcoming. For bandwidth measurements to be stable and reliable, Q must remain in service for a much longer time than that needed to serve a single I/O request. Unfortunately, this does not hold with many workloads. This commit addresses this issue by changing the way the amount of injection allowed is dynamically computed. It tunes injection as a function of the service times of single I/O requests of Q, instead of Q's bandwidth. Single-request service times are evidently meaningful even if Q gets very few I/O requests completed while it is in service. As a testbed for this new solution, we measured the throughput reached by BFQ for one of the nastiest workloads and configurations for this scheduler: the workload generated by the dbench test (in the Phoronix suite), with 6 clients, on a filesystem with journaling, and with the journaling daemon enjoying a higher weight than normal processes. With this commit, the throughput grows from ~100 MB/s to ~150 MB/s on a PLEXTOR PX-256M5. Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by: Francesco Pollicino <fra.fra.800@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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