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  1. 20 Oct, 2021 4 commits
  3. 19 Oct, 2021 3 commits
    • Jens Axboe's avatar
      nvme: don't memset() the normal read/write command · a9a7e30f
      Jens Axboe authored 
      This memset in the fast path costs a lot of cycles on my setup. Here's a
top-of-profile of doing ~6.7M IOPS:

+    5.90%  io_uring  [nvme]            [k] nvme_queue_rq
+    5.32%  io_uring  [nvme_core]       [k] nvme_setup_cmd
+    5.17%  io_uring  [kernel.vmlinux]  [k] io_submit_sqes
+    4.97%  io_uring  [kernel.vmlinux]  [k] blkdev_direct_IO

and a perf diff with this patch:

     0.92%     +4.40%  [nvme_core]       [k] nvme_setup_cmd

reducing it from 5.3% to only 0.9%. This takes it from the 2nd most
cycle consumer to something that's mostly irrelevant.
Reviewed-by: default avatarChaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      a9a7e30f
    • Jens Axboe's avatar
      nvme: move command clear into the various setup helpers · 9c3d2929
      Jens Axboe authored 
      We don't have to worry about doing extra memsets by moving it outside
the protection of RQF_DONTPREP, as nvme doesn't do partial completions.

This is in preparation for making the read/write fast path not do a full
memset of the command.
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      9c3d2929
    • Michael Schmitz's avatar
      block: ataflop: fix breakage introduced at blk-mq refactoring · 86d46fda
      Michael Schmitz authored 
      Refactoring of the Atari floppy driver when converting to blk-mq
has broken the state machine in not-so-subtle ways:

finish_fdc() must be called when operations on the floppy device
have completed. This is crucial in order to relase the ST-DMA
lock, which protects against concurrent access to the ST-DMA
controller by other drivers (some DMA related, most just related
to device register access - broken beyond compare, I know).

When rewriting the driver's old do_request() function, the fact
that finish_fdc() was called only when all queued requests had
completed appears to have been overlooked. Instead, the new
request function calls finish_fdc() immediately after the last
request has been queued. finish_fdc() executes a dummy seek after
most requests, and this overwrites the state machine's interrupt
hander that was set up to wait for completion of the read/write
request just prior. To make matters worse, finish_fdc() is called
before device interrupts are re-enabled, making certain that the
read/write interupt is missed.

Shifting the finish_fdc() call into the read/write request
completion handler ensures the driver waits for the request to
actually complete. With a queue depth of 2, we won't see long
request sequences, so calling finish_fdc() unconditionally just
adds a little overhead for the dummy seeks, and keeps the code
simple.

While we're at it, kill ataflop_commit_rqs() which does nothing
but run finish_fdc() unconditionally, again likely wiping out an
in-flight request.
Signed-off-by: default avatarMichael Schmitz <schmitzmic@gmail.com>
Fixes: 6ec3938c ("ataflop: convert to blk-mq")
CC: linux-block@vger.kernel.org
CC: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Link: https://lore.kernel.org/r/20211019061321.26425-1-schmitzmic@gmail.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
      86d46fda
  5. 18 Oct, 2021 33 commits
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