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  1. 14 Sep, 2019 1 commit
  3. 12 Sep, 2019 2 commits
    • Jens Axboe's avatar
      io_uring: make sqpoll wakeup possible with getevents · b2a9eada
      Jens Axboe authored 
      The way the logic is setup in io_uring_enter() means that you can't wake
up the SQ poller thread while at the same time waiting (or polling) for
completions afterwards. There's no reason for that to be the case.
Reported-by: default avatarLewis Baker <lbaker@fb.com>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      b2a9eada
    • Jens Axboe's avatar
      io_uring: extend async work merging · 6d5d5ac5
      Jens Axboe authored 
      We currently merge async work items if we see a strict sequential hit.
This helps avoid unnecessary workqueue switches when we don't need
them. We can extend this merging to cover cases where it's not a strict
sequential hit, but the IO still fits within the same page. If an
application is doing multiple requests within the same page, we don't
want separate workers waiting on the same page to complete IO. It's much
faster to let the first worker bring in the page, then operate on that
page from the same worker to complete the next request(s).
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      6d5d5ac5
  5. 10 Sep, 2019 3 commits
    • Jens Axboe's avatar
      io_uring: limit parallelism of buffered writes · 54a91f3b
      Jens Axboe authored 
      All the popular filesystems need to grab the inode lock for buffered
writes. With io_uring punting buffered writes to async context, we
observe a lot of contention with all workers hamming this mutex.

For buffered writes, we generally don't need a lot of parallelism on
the submission side, as the flushing will take care of that for us.
Hence we don't need a deep queue on the write side, as long as we
can safely punt from the original submission context.

Add a workqueue with a limit of 2 that we can use for buffered writes.
This greatly improves the performance and efficiency of higher queue
depth buffered async writes with io_uring.
Reported-by: default avatarAndres Freund <andres@anarazel.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      54a91f3b
    • Jens Axboe's avatar
      io_uring: add io_queue_async_work() helper · 18d9be1a
      Jens Axboe authored 
      Add a helper for queueing a request for async execution, in preparation
for optimizing it.

No functional change in this patch.
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      18d9be1a
    • Jens Axboe's avatar
      io_uring: optimize submit_and_wait API · c5766668
      Jens Axboe authored 
      For some applications that end up using a submit-and-wait type of
approach for certain batches of IO, we can make that a bit more
efficient by allowing the application to block for the last IO
submission. This prevents an async when we don't need it, as the
application will be blocking for the completion event(s) anyway.

Typical use cases are using the liburing
io_uring_submit_and_wait() API, or just using io_uring_enter()
doing both submissions and completions. As a specific example,
RocksDB doing MultiGet() is sped up quite a bit with this
change.
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      c5766668
  7. 09 Sep, 2019 2 commits
    • Jackie Liu's avatar
      io_uring: add support for link with drain · 4fe2c963
      Jackie Liu authored 
      To support the link with drain, we need to do two parts.

There is an sqes:

    0     1     2     3     4     5     6
 +-----+-----+-----+-----+-----+-----+-----+
 |  N  |  L  |  L  | L+D |  N  |  N  |  N  |
 +-----+-----+-----+-----+-----+-----+-----+

First, we need to ensure that the io before the link is completed,
there is a easy way is set drain flag to the link list's head, so
all subsequent io will be inserted into the defer_list.

	+-----+
    (0) |  N  |
	+-----+
           |          (2)         (3)         (4)
	+-----+     +-----+     +-----+     +-----+
    (1) | L+D | --> |  L  | --> | L+D | --> |  N  |
	+-----+     +-----+     +-----+     +-----+
           |
	+-----+
    (5) |  N  |
	+-----+
           |
	+-----+
    (6) |  N  |
	+-----+

Second, ensure that the following IO will not be completed first,
an easy way is to create a mirror of drain io and insert it into
defer_list, in this way, as long as drain io is not processed, the
following io in the defer_list will not be actively process.

	+-----+
    (0) |  N  |
	+-----+
           |          (2)         (3)         (4)
	+-----+     +-----+     +-----+     +-----+
    (1) | L+D | --> |  L  | --> | L+D | --> |  N  |
	+-----+     +-----+     +-----+     +-----+
           |
	+-----+
   ('3) |  D  |   <== This is a shadow of (3)
	+-----+
           |
	+-----+
    (5) |  N  |
	+-----+
           |
	+-----+
    (6) |  N  |
	+-----+
Signed-off-by: default avatarJackie Liu <liuyun01@kylinos.cn>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      4fe2c963
    • Jackie Liu's avatar
      io_uring: fix wrong sequence setting logic · 8776f3fa
      Jackie Liu authored 
      Sqo_thread will get sqring in batches, which will cause
ctx->cached_sq_head to be added in batches. if one of these
sqes is set with the DRAIN flag, then he will never get a
chance to process, and finally sqo_thread will not exit.

Fixes: de0617e4 ("io_uring: add support for marking commands as draining")
Signed-off-by: default avatarJackie Liu <liuyun01@kylinos.cn>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      8776f3fa
  9. 06 Sep, 2019 1 commit
    • Jens Axboe's avatar
      io_uring: expose single mmap capability · ac90f249
      Jens Axboe authored 
      After commit 75b28aff we can get by with just a single mmap to
map both the sq and cq ring. However, userspace doesn't know that.

Add a features variable to io_uring_params, and notify userspace
that the kernel has this ability. This can then be used in liburing
(or in applications directly) to avoid the second mmap.
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      ac90f249
  11. 27 Aug, 2019 2 commits
  13. 25 Aug, 2019 22 commits
  15. 24 Aug, 2019 7 commits
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