The patch titled
aio: only account I/O wait time in read_events if there are active requests
has been added to the -mm tree. Its filename is
aio-only-account-i-o-wait-time-in-read_events-if-there-are-active-requests.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: aio: only account I/O wait time in read_events if there are active requests
From: Jeff Moyer <jmoyer@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Zach Brown <zach.brown@xxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Jeff Dike <jdike@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/aio.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN fs/aio.c~aio-only-account-i-o-wait-time-in-read_events-if-there-are-active-requests fs/aio.c
--- a/fs/aio.c~aio-only-account-i-o-wait-time-in-read_events-if-there-are-active-requests
+++ a/fs/aio.c
@@ -1161,7 +1161,12 @@ retry:
ret = 0;
if (to.timed_out) /* Only check after read evt */
break;
- io_schedule();
+ /* 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;
_
Patches currently in -mm which might be from jmoyer@xxxxxxxxxx are
aio-only-account-i-o-wait-time-in-read_events-if-there-are-active-requests.patch
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