6.14-stable review patch. If anyone has any objections, please let me know.
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From: Max Kellermann max.kellermann@ionos.com
[ Upstream commit 486ba4d84d62e92716cd395c4b1612b8ce70a257 ]
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@gmail.com Signed-off-by: Max Kellermann max.kellermann@ionos.com Link: https://lore.kernel.org/r/20250128133927.3989681-6-max.kellermann@ionos.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- 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 d1eaa3e39cd5f..24f06fba43096 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -599,7 +599,9 @@ 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);