On Mon, 2006-01-16 at 09:43 +0100, Jens Axboe wrote:
> On Fri, Jan 13 2006, Andrew Morton wrote:
> > Mingming Cao <[email protected]> wrote:
> > >
> > > On 2.6.14, the
> > > fall back io scheduler (if the chosen io scheduler is not found) is set
> > > to the default io scheduler (anticipatory, in this case), but since
> > > 2.6.15-rc1, this semanistic is changed to fall back to noop.
> >
> > OK. And I assume that AS wasn't compiled, so that's why it fell back?
> >
> > I actually thought that elevator= got removed, now we have
> > /sys/block/sda/queue/scheduler. But I guess that's not very useful with
> > CONFIG_SYSFS=n.
> >
> > > Is there any reason to fall back to noop instead of as? It seems
> > > anticipatory is much better than noop for ext3 with large sequential
> > > write tests (i.e, 1G dd test) ...
> >
> > I suspect that was an accident. Jens?
>
> It is, it makes more sense to fallback to the default of course.
>
How about this one?
In the case the chosen io scheduler (elevator = "xxx") is not on the
registered list, fall back to default scheduler makes more sense.
Signed-off-by: Mingming Cao <[email protected]>
---
linux-2.6.15-ming/block/elevator.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff -puN block/elevator.c~default-fall-back-scheduler-fix
block/elevator.c
--- linux-2.6.15/block/elevator.c~default-fall-back-scheduler-fix
2006-01-16 11:42:04.000446588 -0800
+++ linux-2.6.15-ming/block/elevator.c 2006-01-16 11:42:41.145131615
-0800
@@ -151,12 +151,12 @@ static void elevator_setup_default(void)
strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);
/*
- * If the given scheduler is not available, fall back to no-op.
+ * If the given scheduler is not available, fall back to default.
*/
if ((e = elevator_find(chosen_elevator)))
elevator_put(e);
else
- strcpy(chosen_elevator, "noop");
+ strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);
}
static int __init elevator_setup(char *str)
_
-
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