Re: 2.6.12-rc6-mm1 & 2K lun testing

Andrew Morton
2005-06-17T00:51:30Z

Badari Pulavarty <pbadari@us.ibm.com> wrote:
>
> > Try this:
> >
> > diff -puN mm/page-writeback.c~a mm/page-writeback.c
> > --- 25/mm/page-writeback.c~a Thu Jun 16 13:36:29 2005
> > +++ 25-akpm/mm/page-writeback.c Thu Jun 16 13:36:54 2005
> > @@ -501,6 +501,8 @@ void laptop_sync_completion(void)
> >
> > static void set_ratelimit(void)
> > {
> > + ratelimit_pages = 32;
> > + return;
> > ratelimit_pages = total_pages / (num_online_cpus() * 32);
> > if (ratelimit_pages < 16)
> > ratelimit_pages = 16;
> > _
> >
>
> Wow !! Reducing the dirty ratios and the above patch did the trick.
> Instead of 100% sys CPU, now I have only 50% in sys.

It shouldn't be necessary to do both. Either the patch or the tuning
should fix it. Please confirm.

Also please determine whether the deep CFQ queue depth is a problem when
the VFS tuning/patching is in place.

IOW: let's work out which of these three areas needs to be addressed.