io_uring: speedup provided buffer handling
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>
1 file changed
