Previously, the `hash` variable was initialized with `-1` and only
updated by io_get_next_work() if the current work was hashed. Commit
60cf46ae6054 ("io-wq: hash dependent work") changed this to always
call io_get_work_hash() even if the work was not hashed. This caused
the `hash != -1U` check to always be true, adding some overhead for
the `hash->wait` code.
This patch fixes the regression by checking the `IO_WQ_WORK_HASHED`
flag.
Perf diff for a flood of `IORING_OP_NOP` with `IOSQE_ASYNC`:
38.55% -1.57% [kernel.kallsyms] [k] queued_spin_lock_slowpath
6.86% -0.72% [kernel.kallsyms] [k] io_worker_handle_work
0.10% +0.67% [kernel.kallsyms] [k] put_prev_entity
1.96% +0.59% [kernel.kallsyms] [k] io_nop_prep
3.31% -0.51% [kernel.kallsyms] [k] try_to_wake_up
7.18% -0.47% [kernel.kallsyms] [k] io_wq_free_work
Fixes: 60cf46ae6054 ("io-wq: hash dependent work")
Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
---
io_uring/io-wq.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index ba9974e6f521..6e31f312b61a 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -604,7 +604,9 @@ static void io_worker_handle_work(struct io_wq_acct *acct,
do {
struct io_wq_work *next_hashed, *linked;
unsigned int work_flags = atomic_read(&work->flags);
- unsigned int hash = __io_get_work_hash(work_flags);
+ unsigned int hash = __io_wq_is_hashed(work_flags)
+ ? __io_get_work_hash(work_flags)
+ : -1U;
next_hashed = wq_next_work(work);
--
2.45.2
