Re: objrmap and vmtruncate

Andrew Morton
2003-04-05T03:22:01Z

"Martin J. Bligh" <mbligh@aracnet.com> wrote:
>
> > objrmap does not seem to help. Page clustering might, but is unlikely to
> > be enabled on the machines which actually care about the overhead.
>
> eh? Not sure what you mean by that. It helped massively ...
> diffprofile from kernbench showed:
>
> -4666 -74.9% page_add_rmap
> -10666 -92.0% page_remove_rmap
>
> I'd say that about an 85% reduction in cost is pretty damned fine ;-)
> And that was about a 20% overall reduction in the system time for the
> test too ... that was all for partial objrmap (file backed, not anon).
>

In the test I use (my patch management scripts, which is basically bash
forking its brains out) objrmap reclaims only 30-50% of the rmap CPU
overhead.

Maybe you had a very high sharing level.