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authorJeff Moyer <jmoyer@redhat.com>2007-12-04 23:45:02 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-12-05 09:21:18 -0800
commite00ba3dae077f54cfd2af42e939a618caa7a3bca (patch)
treeeb2f29fe8df7cb29be7d1bdda8dabe825f30f182 /fs/aio.c
parente3c0ac04f980750a368f7cd5f1b8d1d2cdc1f735 (diff)
downloadlwn-e00ba3dae077f54cfd2af42e939a618caa7a3bca.tar.gz
lwn-e00ba3dae077f54cfd2af42e939a618caa7a3bca.zip
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>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/aio.c b/fs/aio.c
index f12db415c0f6..9dec7d2d546e 100644
--- a/fs/aio.c
+++ b/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;