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io_uring/rsrc: optimise single entry advance

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Iterating within the first bvec entry should be essentially free, but we
use iov_iter_advance() for that, which shows up in benchmark profiles
taking up to 0.5% of CPU. Replace it with a hand coded version.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2023-02-22 14:36:50 +00:00 committed by Jens Axboe
parent edd4782696
commit b000ae0ec2
1 changed files with 4 additions and 1 deletions
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io_uring/rsrc.c
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@ -1364,7 +1364,10 @@ int io_import_fixed(int ddir, struct iov_iter *iter,
const struct bio_vec *bvec = imu->bvec;
if (offset <= bvec->bv_len) {
iov_iter_advance(iter, offset);
iter->bvec = bvec;
iter->nr_segs = bvec->bv_len;
iter->count -= offset;
iter->iov_offset = offset;
} else {
unsigned long seg_skip;