Commit e00ba3da authored Dec 04, 2007 by Jeff Moyer Committed by Linus Torvalds Dec 05, 2007

aio: only account I/O wait time in read_events if there are active requests



On 2.6.24, top started showing 100% iowait on one CPU when a UML instance was
running (but completely idle).  The UML code sits in io_getevents waiting for
an event to be submitted and completed.

Fix this by checking ctx->reqs_active before scheduling to determine whether
or not we are waiting for I/O.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e3c0ac04

fs/aio.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1161,7 +1161,12 @@ retry:
		ret = 0;
		if (to.timed_out) /* Only check after read evt */
		break;
		/* Try to only show up in io wait if there are ops
		* in flight */
		if (ctx->reqs_active)
		io_schedule();
		else
		schedule();
		if (signal_pending(tsk)) {
		ret = -EINTR;
		break;

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