On Thu, Jan 19 2006, Nate Diller wrote:
> On 1/16/06, Jens Axboe <[email protected]> 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.
>
> Not an accident at all, actually, because the original patch i
> submitted allowed you to select a scheduler as 'default' even if it
> were compiled as a module in kconfig. Since noop is guaranteed to be
> present in any system, it is the obvious choice if the chosen or
> default scheduler is not loaded.
Yes and that was a bug in that patch. The default scheduler must be
builtin, that's a given. The Kconfig rules should make a default
selection as a module illegal. And they do, they have since been fixed.
> If you change it to fall back to the default, it will oops if the
> default is not available.
It must be.
--
Jens Axboe
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
