Rohit Seth <[email protected]> wrote:
>
> On Wed, 2005-11-23 at 11:30 -0800, Christoph Lameter wrote:
> > On Tue, 22 Nov 2005, Rohit Seth wrote:
> >
> > > [PATCH]: This patch free pages (pcp->batch from each list at a time) from
> > > local pcp lists when a higher order allocation request is not able to
> > > get serviced from global free_list.
> >
> > Ummm.. One controversial idea: How about removing the complete pcp
> > subsystem? Last time we disabled pcps we saw that the effect
> > that it had was within noise ratio on AIM7. The lru lock taken without
> > pcp is in the local zone and thus rarely contended.
>
> Oh please stop.
>
> This per_cpu_pagelist is one great logic that has got added in
> allocator. Besides providing pages without the need to acquire the zone
> lock, it is one single main reason the coloring effect is drastically
> reduced in 2.6 (over 2.4) based kernels.
>
hm. Before it was merged in 2.5.x, the feature was very marginal from a
performance POV in my testing on 4-way.
I was able to demonstrate a large (~60%?) speedup in one microbenckmark
which consisted of four processes writing 16k to a file and truncating it
back to zero again. That gain came from the cache warmth effect, which is
the other benefit which these cpu-local pages are supposed to provide.
I don't think Martin was able to demonstrate much benefit from the lock
contention reduction on 16-way NUMAQ either.
So I dithered for months and it was a marginal merge, so it's appropriate
to justify the continued presence of the code.
We didn't measure for any coloring effects though. In fact, I didn't know
that this feature actually provided any benefit in that area.
-
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]