- 07 10月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
We currently divide the queue depth by 4 as our batch wakeup count, but we split the wakeups over BT_WAIT_QUEUES number of wait queues. This defaults to 8. If the product of the resulting batch wake count and BT_WAIT_QUEUES is higher than the device queue depth, we can get into a situation where a task goes to sleep waiting for a request, but never gets woken up. Reported-by: NBart Van Assche <bvanassche@acm.org> Fixes: 4bb659b1 Cc: stable@kernel.org Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 23 9月, 2014 1 次提交
-
-
由 Christoph Hellwig 提交于
Don't do a kmalloc from timer to handle timeouts, chances are we could be under heavy load or similar and thus just miss out on the timeouts. Fortunately it is very easy to just iterate over all in use tags, and doing this properly actually cleans up the blk_mq_busy_iter API as well, and prepares us for the next patch by passing a reserved argument to the iterator. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 18 6月, 2014 3 次提交
-
-
由 Alexander Gordeev 提交于
This update fixes few issues in bt_get() function: - list_empty(&wait.task_list) check is not protected; - was_empty check is always true which results in *every* thread entering the loop resets bt_wait_state::wait_cnt counter rather than every bt->wake_cnt'th thread; - 'bt_wait_state::wait_cnt' counter update is redundant, since it also gets reset in bt_clear_tag() function; Cc: Christoph Hellwig <hch@infradead.org> Cc: Ming Lei <tom.leiming@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: NAlexander Gordeev <agordeev@redhat.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
由 Alexander Gordeev 提交于
This piece of code in bt_clear_tag() function is racy: bs = bt_wake_ptr(bt); if (bs && atomic_dec_and_test(&bs->wait_cnt)) { atomic_set(&bs->wait_cnt, bt->wake_cnt); wake_up(&bs->wait); } Since nothing prevents bt_wake_ptr() from returning the very same 'bs' address on multiple CPUs, the following scenario is possible: CPU1 CPU2 ---- ---- 0. bs = bt_wake_ptr(bt); bs = bt_wake_ptr(bt); 1. atomic_dec_and_test(&bs->wait_cnt) 2. atomic_dec_and_test(&bs->wait_cnt) 3. atomic_set(&bs->wait_cnt, bt->wake_cnt); If the decrement in [1] yields zero then for some amount of time the decrement in [2] results in a negative/overflow value, which is not expected. The follow-up assignment in [3] overwrites the invalid value with the batch value (and likely prevents the issue from being severe) which is still incorrect and should be a lesser. Cc: Ming Lei <tom.leiming@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: NAlexander Gordeev <agordeev@redhat.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
由 Alexander Gordeev 提交于
Fix racy updates of shared blk_mq_bitmap_tags::wake_index and blk_mq_hw_ctx::wake_index fields. Cc: Ming Lei <tom.leiming@gmail.com> Signed-off-by: NAlexander Gordeev <agordeev@redhat.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 04 6月, 2014 1 次提交
-
-
由 Ming Lei 提交于
blk_mq_put_ctx() has to be called before io_schedule() in bt_get(). This patch fixes the problem by taking similar approach from percpu_ida allocation for the situation. Signed-off-by: NMing Lei <tom.leiming@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 29 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
None of the blk-mq files have an explanatory comment at the top for what that particular file does. Add that and add appropriate copyright notices as well. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 28 5月, 2014 1 次提交
-
-
由 Christoph Hellwig 提交于
The current logic for blocking tag allocation is rather confusing, as we first allocated and then free again a tag in blk_mq_wait_for_tags, just to attempt a non-blocking allocation and then repeat if someone else managed to grab the tag before us. Instead change blk_mq_alloc_request_pinned to simply do a blocking tag allocation itself and use the request we get back from it. Signed-off-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 24 5月, 2014 1 次提交
-
-
由 Sam Bradshaw 提交于
Export the blk-mq in-flight tag iterator for driver consumption. This is particularly useful in exception paths or SRSI where in-flight IOs need to be cancelled and/or reissued. The NVMe driver conversion will use this. Signed-off-by: NSam Bradshaw <sbradshaw@micron.com> Signed-off-by: NMatias Bjørling <m@bjorling.me> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 21 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
For request_fn based devices, the block layer exports a 'nr_requests' file through sysfs to allow adjusting of queue depth on the fly. Currently this returns -EINVAL for blk-mq, since it's not wired up. Wire this up for blk-mq, so that it now also always dynamic adjustments of the allowed queue depth for any given block device managed by blk-mq. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 20 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
We will use it for the pending list in blk-mq core as well. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 14 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
This adds support for active queue tracking, meaning that the blk-mq tagging maintains a count of active users of a tag set. This allows us to maintain a notion of fairness between users, so that we can distribute the tag depth evenly without starving some users while allowing others to try unfair deep queues. If sharing of a tag set is detected, each hardware queue will track the depth of its own queue. And if this exceeds the total depth divided by the number of active queues, the user is actively throttled down. The active queue count is done lazily to avoid bouncing that data between submitter and completer. Each hardware queue gets marked active when it allocates its first tag, and gets marked inactive when 1) the last tag is cleared, and 2) the queue timeout grace period has passed. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 11 5月, 2014 4 次提交
-
-
由 Ming Lei 提交于
Both nr_cache and nr_tags arn't needed for bitmap tag anymore. Signed-off-by: NMing Lei <tom.leiming@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
由 Ming Lei 提交于
The selected tag should be selected at random between 0 and (depth - 1) with probability 1/depth, instead between 0 and (depth - 2) with probability 1/(depth - 1). Signed-off-by: NMing Lei <tom.leiming@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
由 Ming Lei 提交于
The barrier isn't necessary because both atomic_dec_and_test() and wake_up() implicate one barrier. Signed-off-by: NMing Lei <tom.leiming@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
由 Ming Lei 提交于
The unlock memory barrier need to order access to req in free path and clearing tag bit, otherwise either request free path may see a allocated request, or initialized request in allocate path might be modified by the ongoing free path. Signed-off-by: NMing Lei <tom.leiming@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 10 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
For best performance, spreading tags over multiple cachelines makes the tagging more efficient on multicore systems. But since we have 8 * sizeof(unsigned long) tags per cacheline, we don't always get a nice spread. Attempt to spread the tags over at least 4 cachelines, using fewer number of bits per unsigned long if we have to. This improves tagging performance in setups with 32-128 tags. For higher depths, the spread is the same as before (BITS_PER_LONG tags per cacheline). Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 09 5月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
blk-mq currently uses percpu_ida for tag allocation. But that only works well if the ratio between tag space and number of CPUs is sufficiently high. For most devices and systems, that is not the case. The end result if that we either only utilize the tag space partially, or we end up attempting to fully exhaust it and run into lots of lock contention with stealing between CPUs. This is not optimal. This new tagging scheme is a hybrid bitmap allocator. It uses two tricks to both be SMP friendly and allow full exhaustion of the space: 1) We cache the last allocated (or freed) tag on a per blk-mq software context basis. This allows us to limit the space we have to search. The key element here is not caching it in the shared tag structure, otherwise we end up dirtying more shared cache lines on each allocate/free operation. 2) The tag space is split into cache line sized groups, and each context will start off randomly in that space. Even up to full utilization of the space, this divides the tag users efficiently into cache line groups, avoiding dirtying the same one both between allocators and between allocator and freeer. This scheme shows drastically better behaviour, both on small tag spaces but on large ones as well. It has been tested extensively to show better performance for all the cases blk-mq cares about. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 30 4月, 2014 1 次提交
-
-
由 Jens Axboe 提交于
blk_mq_wait_for_tags() is only able to wait for "normal" tags, not reserved tags. Pass in which one we should attempt to get a tag for, so that waiting for reserved tags will work. Reserved tags are used for internal commands, which are usually serialized. Hence no waiting generally takes place, but we should ensure that it actually works if users need that functionality. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 16 4月, 2014 1 次提交
-
-
由 Christoph Hellwig 提交于
Add a new blk_mq_tag_set structure that gets set up before we initialize the queue. A single blk_mq_tag_set structure can be shared by multiple queues. Signed-off-by: NChristoph Hellwig <hch@lst.de> Modular export of blk_mq_{alloc,free}_tagset added by me. Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 11 2月, 2014 1 次提交
-
-
由 Masanari Iida 提交于
cppcheck detected following format string mismatch. [blk-mq-tag.c:201]: (warning) %u in format string (no. 1) requires 'unsigned int' but the argument type is 'int'. Change "cpu" from int to unsigned int, because the cpu never become minus value. Signed-off-by: NMasanari Iida <standby24x7@gmail.com> Signed-off-by: NJens Axboe <axboe@fb.com>
-
- 24 1月, 2014 1 次提交
-
-
由 Kent Overstreet 提交于
This patch changes percpu_ida_alloc() + callers to accept task state bitmask for prepare_to_wait() for code like target/iscsi that needs it for interruptible sleep, that is provided in a subsequent patch. It now expects TASK_UNINTERRUPTIBLE when the caller is able to sleep waiting for a new tag, or TASK_RUNNING when the caller cannot sleep, and is forced to return a negative value when no tags are available. v2 changes: - Include blk-mq + tcm_fc + vhost/scsi + target/iscsi changes - Drop signal_pending_state() call v3 changes: - Only call prepare_to_wait() + finish_wait() when != TASK_RUNNING (PeterZ) Reported-by: NLinus Torvalds <torvalds@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: NKent Overstreet <kmo@daterainc.com> Cc: <stable@vger.kernel.org> #3.12+ Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>
-
- 25 10月, 2013 1 次提交
-
-
由 Jens Axboe 提交于
Linux currently has two models for block devices: - The classic request_fn based approach, where drivers use struct request units for IO. The block layer provides various helper functionalities to let drivers share code, things like tag management, timeout handling, queueing, etc. - The "stacked" approach, where a driver squeezes in between the block layer and IO submitter. Since this bypasses the IO stack, driver generally have to manage everything themselves. With drivers being written for new high IOPS devices, the classic request_fn based driver doesn't work well enough. The design dates back to when both SMP and high IOPS was rare. It has problems with scaling to bigger machines, and runs into scaling issues even on smaller machines when you have IOPS in the hundreds of thousands per device. The stacked approach is then most often selected as the model for the driver. But this means that everybody has to re-invent everything, and along with that we get all the problems again that the shared approach solved. This commit introduces blk-mq, block multi queue support. The design is centered around per-cpu queues for queueing IO, which then funnel down into x number of hardware submission queues. We might have a 1:1 mapping between the two, or it might be an N:M mapping. That all depends on what the hardware supports. blk-mq provides various helper functions, which include: - Scalable support for request tagging. Most devices need to be able to uniquely identify a request both in the driver and to the hardware. The tagging uses per-cpu caches for freed tags, to enable cache hot reuse. - Timeout handling without tracking request on a per-device basis. Basically the driver should be able to get a notification, if a request happens to fail. - Optional support for non 1:1 mappings between issue and submission queues. blk-mq can redirect IO completions to the desired location. - Support for per-request payloads. Drivers almost always need to associate a request structure with some driver private command structure. Drivers can tell blk-mq this at init time, and then any request handed to the driver will have the required size of memory associated with it. - Support for merging of IO, and plugging. The stacked model gets neither of these. Even for high IOPS devices, merging sequential IO reduces per-command overhead and thus increases bandwidth. For now, this is provided as a potential 3rd queueing model, with the hope being that, as it matures, it can replace both the classic and stacked model. That would get us back to having just 1 real model for block devices, leaving the stacked approach to dm/md devices (as it was originally intended). Contributions in this patch from the following people: Shaohua Li <shli@fusionio.com> Alexander Gordeev <agordeev@redhat.com> Christoph Hellwig <hch@infradead.org> Mike Christie <michaelc@cs.wisc.edu> Matias Bjorling <m@bjorling.me> Jeff Moyer <jmoyer@redhat.com> Acked-by: NChristoph Hellwig <hch@lst.de> Signed-off-by: NJens Axboe <axboe@kernel.dk>
-