On Mon, 2005-07-11 at 15:41 -0700, Andrew Morton wrote:
> Steven Rostedt <[email protected]> wrote:
> >
> > I noticed that the code in commit.c of the jbd system can waste CPU
> > cycles.
>
> How did you notice? By code inspection or by runtime observation? If the
> latter, please share.
Argh! I just realize that this problem is really more in Ingo's RT
kernel, but I assumed that it was a problem in vanilla since the code is
more from the vanilla kernel. With Ingo's spin_locks as mutexes, this
creates a problem on UP, but your are right, this is not a problem for
vanilla UP.
> Yeah. But these _are_ spinlocks, so spinning is what's supposed to happen.
> Maybe we should dump that silly schedule() and just do cpu_relax().
> Although I do recall once theorising that the time we spend in the
> schedule() might be preventing livelocks.
>
As mentioned above, this was a confusion of paradigms. I just got back
from Europe, so I'm blaming this on jetlag!
OK a cpu_relax() may be better. So here it is :-)
Signed-off-by: Steven Rostedt <[email protected]>
---
--- a/fs/jbd/commit.c 2005-07-11 17:51:37.000000000 -0400
+++ b/fs/jbd/commit.c 2005-07-11 19:05:35.000000000 -0400
@@ -87,7 +87,7 @@ static int inverted_lock(journal_t *jour
{
if (!jbd_trylock_bh_state(bh)) {
spin_unlock(&journal->j_list_lock);
- schedule();
+ cpu_relax();
return 0;
}
return 1;
-
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