io_uring: speedup provided buffer handling

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In testing high frequency workloads with provided buffers, we spend a
lot of time in allocating and freeing the buffer units themselves.
Rather than repeatedly free and alloc them, add a recycling cache
instead. There are two caches:

- ctx->io_buffers_cache. This is the one we grab from in the submission
  path, and it's protected by ctx->uring_lock. For inline completions,
  we can recycle straight back to this cache and not need any extra
  locking.

- ctx->io_buffers_comp. If we're not under uring_lock, then we use this
  list to recycle buffers. It's protected by the completion_lock.

On adding a new buffer, check io_buffers_cache. If it's empty, check if
we can splice entries from the io_buffers_comp_cache.

This reduces about 5-10% of overhead from provided buffers, bringing it
pretty close to the non-provided path.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

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This commit is contained in:

Jens Axboe 2022-03-08 17:46:52 -07:00

parent e7a6c00dc7

commit cc3cec8367

1 changed files with 117 additions and 22 deletions

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fs/io_uring.c

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