Re: Linux 2.6.29

Andrew Morton
2009-03-27T00:15:01Z

On Wed, 25 Mar 2009 16:23:08 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:

>
>
> On Wed, 25 Mar 2009, Theodore Tso wrote:
> > >
> > > The problem being that unlike the ratio, there's no sane default value
> > > that you can at least argue is not _entirely_ pointless.
> >
> > Well, if the maximum time that someone wants to wait for an fsync() to
> > return is one second, and the RAID array can write 100MB/sec
>
> How are you going to tell the kernel that the RAID array can write
> 100MB/s?
>
> The kernel has no idea.
>

userspace can do it quite easily. Run a self-tuning script after
installation and when the disk hardware changes significantly.

It is very disappointing that nobody appears to have attempted to do
_any_ sensible tuning of these controls in all this time - we just keep
thrashing around trying to pick better magic numbers in the base kernel.

Maybe we should set the tunables to 99.9% to make it suck enough to
motivate someone.