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@xxxxxxxxx>
---
io_uring/rsrc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 53845e496881..ebbd2cea7582 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -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;
--
2.39.1
