On 2.6.24, top started showing 100% iowait on one CPU when a UML
instance was running (but completely idle). I've traced it to this
commit. Reverting it cures the problem.
Miklos
commit 41d10da3717409de33d5441f2f6d8f072ab3fbb6
Author: Jeff Moyer <[email protected]>
Date: Tue Oct 16 23:27:20 2007 -0700
aio: account I/O wait time properly
Some months back I proposed changing the schedule() call in
read_events to an io_schedule():
http://osdir.com/ml/linux.kernel.aio.general/2006-10/msg00024.html
This was rejected as there are AIO operations that do not initiate
disk I/O. I've had another look at the problem, and the only AIO
operation that will not initiate disk I/O is IOCB_CMD_NOOP. However,
this command isn't even wired up!
Given that it doesn't work, and hasn't for *years*, I'm going to
suggest again that we do proper I/O accounting when using AIO.
Signed-off-by: Jeff Moyer <[email protected]>
Acked-by: Zach Brown <[email protected]>
Cc: Benjamin LaHaise <[email protected]>
Cc: Suparna Bhattacharya <[email protected]>
Cc: Badari Pulavarty <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/fs/aio.c b/fs/aio.c
index ea2e198..d02f43b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -303,7 +303,7 @@ static void wait_for_all_aios(struct kioctx *ctx)
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
while (ctx->reqs_active) {
spin_unlock_irq(&ctx->ctx_lock);
- schedule();
+ io_schedule();
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
spin_lock_irq(&ctx->ctx_lock);
}
@@ -323,7 +323,7 @@ ssize_t fastcall wait_on_sync_kiocb(struct kiocb *iocb)
set_current_state(TASK_UNINTERRUPTIBLE);
if (!iocb->ki_users)
break;
- schedule();
+ io_schedule();
}
__set_current_state(TASK_RUNNING);
return iocb->ki_user_data;
@@ -1170,7 +1170,7 @@ retry:
ret = 0;
if (to.timed_out) /* Only check after read evt */
break;
- schedule();
+ io_schedule();
if (signal_pending(tsk)) {
ret = -EINTR;
break;
--
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