aio: Skip timer for io_getevents if timeout=0 (5f785de5) · Commits · 戴 / test

In this case, it is basically a polling. Let's not involve timer at all because that would hurt performance for application event loops. In an arbitrary test I've done, io_getevents syscall elapsed time reduces from 50000+ nanoseconds to a few hundereds. Signed-off-by:

Fam Zheng <famz@redhat.com> Signed-off-by:

Benjamin LaHaise <bcrl@kvack.org>

fs/aio.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1253,8 +1253,12 @@ static long read_events(struct kioctx *ctx, long min_nr, long nr,
		* the ringbuffer empty. So in practice we should be ok, but it's
		* something to be aware of when touching this code.
		*/
		if (until.tv64 == 0)
		aio_read_events(ctx, min_nr, nr, event, &ret);
		else
		wait_event_interruptible_hrtimeout(ctx->wait,
		aio_read_events(ctx, min_nr, nr, event, &ret), until);
		aio_read_events(ctx, min_nr, nr, event, &ret),
		until);

		if (!ret && signal_pending(current))
		ret = -EINTR;

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