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io_uring/sqpoll: do the napi busy poll outside the submission block

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there are many small reasons justifying this change.

1. busy poll must be performed even on rings that have no iopoll and no
   new sqe. It is quite possible that a ring configured for inbound
   traffic with multishot be several hours without receiving new request
   submissions
2. NAPI busy poll does not perform any credential validation
3. If the thread is awaken by task work, processing the task work is
   prioritary over NAPI busy loop. This is why a second loop has been
   created after the io_sq_tw() call instead of doing the busy loop in
   __io_sq_thread() outside its credential acquisition block.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Link: https://lore.kernel.org/r/de7679adf1249446bd47426db01d82b9603b7224.1726161831.git.olivier@trillion01.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Olivier Langlois 2024-09-16 15:17:56 -04:00 committed by Jens Axboe
parent 2f6a55e423
commit 53d69bdd5b
1 changed files with 4 additions and 3 deletions
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7
io_uring/sqpoll.c
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@ -196,9 +196,6 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
ret = io_submit_sqes(ctx, to_submit);
mutex_unlock(&ctx->uring_lock);
if (io_napi(ctx))
ret += io_napi_sqpoll_busy_poll(ctx);
if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
wake_up(&ctx->sqo_sq_wait);
if (creds)
@ -323,6 +320,10 @@ static int io_sq_thread(void *data)
if (io_sq_tw(&retry_list, IORING_TW_CAP_ENTRIES_VALUE))
sqt_spin = true;
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
if (io_napi(ctx))
io_napi_sqpoll_busy_poll(ctx);
if (sqt_spin || !time_after(jiffies, timeout)) {
if (sqt_spin) {
io_sq_update_worktime(sqd, &start);