From e00ba3dae077f54cfd2af42e939a618caa7a3bca Mon Sep 17 00:00:00 2001 From: Jeff Moyer Date: Tue, 4 Dec 2007 23:45:02 -0800 Subject: [PATCH] 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 Cc: Zach Brown Cc: Miklos Szeredi Cc: Jeff Dike Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/aio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/aio.c b/fs/aio.c index f12db41..9dec7d2 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; -- 2.7.4