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SubjectRe: Page Faults slower in 2.6.25-rc9 than 2.6.23
On Tue, Apr 29, 2008 at 7:27 PM, Hugh Dickins <hugh@veritas.com> wrote:
> On Tue, 29 Apr 2008, Ross Biro wrote:
> > I don't know if this has been noticed before. I was benchmarking my
> > page table relocation code and I noticed that on 2.6.25-rc9 page
> > faults take 10% more time than on 2.6.22. This is using lmbench
> > running on an intel x86_64 system. The good news is that the page
> > table relocation code now only adds a 1.6% slow down to page faults.
>
> Do you have CONFIG_CGROUP_MEM_RES_CTLR=y in 2.6.25?
> That added about 20% to my lmbench "Page Fault" tests (with
> adverse effect on several others e.g. the fork, exec, sh group).
>

Hmm.. strange.. I don't remember the overhead being so bad (I'll
relook at my old numbers). I'll try and git-bisect this one


> Try the same kernel with boot option "cgroup_disable=memory",
> that should recoup most (but not quite all) of the slowdown;
> or rebuild with n to CGROUP_MEM_RES_CTLR.
>
> But your "Mmap Latency" went up 425% ??
>

That's really way of the mark

> Hugh
>

Balbir


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