- 18 Oct, 2021 40 commits
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Jens Axboe authored
There's currently no way to experiment with polled IO with null_blk, which seems like an oversight. This patch adds support for polled IO. We keep a list of issued IOs on submit, and then process that list when mq_ops->poll() is invoked. A new parameter is added, poll_queues. It defaults to 1 like the submit queues, meaning we'll have 1 poll queue available. Fixes-by:
Bart Van Assche <bvanassche@acm.org> Fixes-by:
Pavel Begunkov <asml.silence@gmail.com> Reviewed-by:
Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Link: https://lore.kernel.org/r/baca710d-0f2a-16e2-60bd-b105b854e0ae@kernel.dkSigned-off-by:
Jens Axboe <axboe@kernel.dk>
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Jens Axboe authored
Trivial to do now, just need our own io_comp_batch on the stack and pass that in to the usual command completion handling. I pondered making this dependent on how many entries we had to process, but even for a single entry there's no discernable difference in performance or latency. Running a sync workload over io_uring: t/io_uring -b512 -d1 -s1 -c1 -p0 -F1 -B1 -n2 /dev/nvme1n1 /dev/nvme2n1 yields the below performance before the patch: IOPS=254820, BW=124MiB/s, IOS/call=1/1, inflight=(1 1) IOPS=251174, BW=122MiB/s, IOS/call=1/1, inflight=(1 1) IOPS=250806, BW=122MiB/s, IOS/call=1/1, inflight=(1 1) and the following after: IOPS=255972, BW=124MiB/s, IOS/call=1/1, inflight=(1 1) IOPS=251920, BW=123MiB/s, IOS/call=1/1, inflight=(1 1) IOPS=251794, BW=122MiB/s, IOS/call=1/1, inflight=(1 1) which definitely isn't slower, about the same if you factor in a bit of variance. For peak performance workloads, benchmarking shows a 2% improvement. Reviewed-by:
Christoph Hellwig <hch@lst.de> Signed-off-by:
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Jens Axboe authored
Wire up using an io_comp_batch for f_op->iopoll(). If the lower stack supports it, we can handle high rates of polled IO more efficiently. This raises the single core efficiency on my system from ~6.1M IOPS to ~6.6M IOPS running a random read workload at depth 128 on two gen2 Optane drives. Reviewed-by:
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Jens Axboe authored
Take advantage of struct io_comp_batch, if passed in to the nvme poll handler. If it's set, rather than complete each request individually inline, store them in the io_comp_batch list. We only do so for requests that will complete successfully, anything else will be completed inline as before. Reviewed-by:
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Jens Axboe authored
Instead of calling blk_mq_end_request() on a single request, add a helper that takes the new struct io_comp_batch and completes any request stored in there. Reviewed-by:
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Jens Axboe authored
sbitmap currently only supports clearing tags one-by-one, add a helper that allows the caller to pass in an array of tags to clear. Signed-off-by: -
Jens Axboe authored
struct io_comp_batch contains a list head and a completion handler, which will allow completions to more effciently completed batches of IO. For now, no functional changes in this patch, we just define the io_comp_batch structure and add the argument to the file_operations iopoll handler. Reviewed-by:
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Jens Axboe authored
Instead of open-coding the list additions, traversal, and removal, provide a basic set of helpers. Suggested-by:
Christoph Hellwig <hch@infradead.org> Signed-off-by:
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Jens Axboe authored
Just like the blk_mq_ctx counterparts, we've got a bunch of counters in here that are only for debugfs and are of questionnable value. They are: - dispatched, index of how many requests were dispatched in one go - poll_{considered,invoked,success}, which track poll sucess rates. We're confident in the iopoll implementation at this point, don't bother tracking these. As a bonus, this shrinks each hardware queue from 576 bytes to 512 bytes, dropping a whole cacheline. Reviewed-by: -
Jens Axboe authored
These were added as part of early days debugging for blk-mq, and they are not really useful anymore. Rather than spend cycles updating them, just get rid of them. As a bonus, this shrinks the per-cpu software queue size from 256b to 192b. That's a whole cacheline less. Reviewed-by:
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Pavel Begunkov authored
Add a local variable for rq_flags, it helps to compile out some of rq_flags reloads. Signed-off-by:
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Pavel Begunkov authored
We should have enough of registers in blk_mq_rq_ctx_init(), store them in local vars, so we don't keep reloading them. note: keeping q->elevator may look unnecessary, but it's also used inside inlined blk_mq_tags_from_data(). Signed-off-by:
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Pavel Begunkov authored
Don't init rq->hash and rq->rb_node in blk_mq_rq_ctx_init() if there is no elevator. Also, move some other initialisers that imply barriers to the end, so the compiler is free to rearrange and optimise other the rest of them. note: fold in a change from Jens leaving queue_list unconditional, as it might lead to problems otherwise. Signed-off-by:
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Jens Axboe authored
Add an rq private RQF_ELV flag, which tells the block layer that this request was initialized on a queue that has an IO scheduler attached. This allows for faster checking in the fast path, rather than having to deference rq->q later on. Elevator switching does full quiesce of the queue before detaching an IO scheduler, so it's safe to cache this in the request itself. Signed-off-by: -
Jens Axboe authored
We set BIO_TRACKED unconditionally when rq_qos_throttle() is called, even though we may not even have an rq_qos handler. Only mark it as TRACKED if it really is potentially tracked. This saves considerable time for the case where the bio isn't tracked: 2.64% -1.65% [kernel.vmlinux] [k] bio_endio Reviewed-by: -
Jens Axboe authored
It's been a while since this was analyzed, move some members around to better flow with the use case. Initial state up top, and queued state after that. This improves my peak case by about 1.5%, from 7750K to 7900K IOPS. Reviewed-by:
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Jens Axboe authored
For some reason we still have them in blk-core, with the rest of the request completion being in blk-mq. That causes and out-of-line call for each completion. Move them into blk-mq.c instead, where they belong. Reviewed-by:
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Jens Axboe authored
We have exactly one caller of this, just get rid of adding the useless function name to the output. Reviewed-by:
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Jens Axboe authored
If we're completing nbytes and nbytes is the size of the bio, don't bother with calling into the iterator increment helpers. Just clear the bio size and we're done. Reviewed-by:
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Pavel Begunkov authored
Convert bdev->bd_disk->queue to bdev_get_queue(), it's uses a cached queue pointer and so is faster. Signed-off-by:
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Pavel Begunkov authored
Convert bdev->bd_disk->queue to bdev_get_queue(), it's uses a cached queue pointer and so is faster. Signed-off-by:
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Pavel Begunkov authored
Convert bdev->bd_disk->queue to bdev_get_queue(), it's uses a cached queue pointer and so is faster. Signed-off-by:
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Pavel Begunkov authored
Convert bdev->bd_disk->queue to bdev_get_queue(), it's uses a cached queue pointer and so is faster. Signed-off-by:
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Pavel Begunkov authored
There are tons of places where we need to get a request_queue only having bdev, which turns into bdev->bd_disk->queue. There are probably a hundred of such places considering inline helpers, and enough of them are in hot paths. Cache queue pointer in struct block_device and make use of it in bdev_get_queue(). Signed-off-by:
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Jens Axboe authored
The fast path is no splitting needed. Separate the handling into a check part we can inline, and an out-of-line handling path if we do need to split. Reviewed-by:
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Jens Axboe authored
This generates a lot better code for me, and bumps performance from 7650K IOPS to 7750K IOPS. Looking at profiles for the run and running perf diff, it confirms that we're now sending a lot less time there: 6.38% -2.80% [kernel.vmlinux] [k] blkdev_direct_IO Taking it from the 2nd most cycle consumer to only the 9th most at 3.35% of the CPU time. Reviewed-by: -
Pavel Begunkov authored
bdev = &BDEV_I(file->f_mapping->host)->bdev Getting struct block_device from a file requires 2 memory dereferences as illustrated above, that takes a toll on performance, so cache it in yet unused file->private_data. That gives a noticeable peak performance improvement. Signed-off-by:
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Christoph Hellwig authored
Set the poll queue flag to enable polling, given that the multipath node just dispatches the bios to a lower queue. Signed-off-by:
Mark Wunderlich <mark.wunderlich@intel.com> Link: https://lore.kernel.org/r/20211012111226.760968-17-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
The poll attribute is a historic artefact from before when we had explicit poll queues that require driver specific configuration. Just print a warning when writing to the attribute. Signed-off-by:
Sagi Grimberg <sagi@grimberg.me> Tested-by:
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Christoph Hellwig authored
Replace the blk_poll interface that requires the caller to keep a queue and cookie from the submissions with polling based on the bio. Polling for the bio itself leads to a few advantages: - the cookie construction can made entirely private in blk-mq.c - the caller does not need to remember the request_queue and cookie separately and thus sidesteps their lifetime issues - keeping the device and the cookie inside the bio allows to trivially support polling BIOs remapping by stacking drivers - a lot of code to propagate the cookie back up the submission path can be removed entirely. Signed-off-by:
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Ming Lei authored
'struct bvec_iter' is embedded into 'struct bio', define it as packed so that we can get one extra 4bytes for other uses without expanding bio. 'struct bvec_iter' is often allocated on stack, so making it packed doesn't affect performance. Also I have run io_uring on both nvme/null_blk, and not observe performance effect in this way. Suggested-by:
Ming Lei <ming.lei@redhat.com> Reviewed-by:
Hannes Reinecke <hare@suse.de> Signed-off-by:
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Christoph Hellwig authored
This flags ensures that the pages will not be reused for non-bio allocations before the end of an RCU grace period. With that we can safely use a RCU lookup for bio polling as long as we are fine with occasionally polling the wrong device. Signed-off-by:
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Christoph Hellwig authored
Unlike the RWF_HIPRI userspace ABI which is intentionally kept vague, the bio flag is specific to the polling implementation, so rename and document it properly. Signed-off-by:
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Christoph Hellwig authored
There is no point in sleeping for the expected I/O completion timeout in the io_uring async polling model as we never poll for a specific I/O. Signed-off-by:
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Christoph Hellwig authored
Switch the boolean spin argument to blk_poll to passing a set of flags instead. This will allow to control polling behavior in a more fine grained way. Signed-off-by:
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Christoph Hellwig authored
Move the trivial check into the only caller. Signed-off-by:
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Christoph Hellwig authored
Merge both functions into their only caller to keep the blk-mq tag to blk_qc_t mapping as private as possible in blk-mq.c. Signed-off-by:
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Christoph Hellwig authored
Factor the code to do the classic full metal polling out of blk_poll into a separate blk_mq_poll_classic helper. Signed-off-by:
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Christoph Hellwig authored
Add a helper to get the hctx from a request_queue and cookie, and fold the blk_qc_t_to_queue_num helper into it as no other callers are left. Signed-off-by:
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Christoph Hellwig authored
syscall-level code can't just poke into the details of the poll cookie, which is private information of the block layer. Signed-off-by:
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