On Wed, Oct 20, 2010 at 12:28:25PM -0700, Greg Stark wrote:
> On Wed, Oct 20, 2010 at 12:17 PM, Greg Stark <gsstark@mit.edu> wrote:
> > I don't think it's a big cost once all the processes
> > have been forked if you're reusing them beyond perhaps slightly more
> > efficient cache usage.
>
> Hm, this site claims to get a 13% win just from the reduced tlb misses
> using a preload hack with Pg 8.2. That would be pretty substantial.
>
> http://oss.linbit.com/hugetlb/
That was my motivation in trying a patch. TLB misses can be a substantial
overhead. I'm not current on the state of play, but working at Sun's
benchmark lab on a DB TPC-B benchmark something for the first generation
of MP systems, something like 30% of all bus traffic was TLB misses. The
next iteration of the hardward had a much larger TLB.
I have a client with 512GB memory systems, currently with 128GB configured
as postgresql buffer cache. Which is 32M TLB entires trying to fit in the
few dozed cpu TLB slots. I suspect there may be some contention.
I'll benchmark of course.
-dg
--
David Gould daveg@sonic.net 510 536 1443 510 282 0869
If simplicity worked, the world would be overrun with insects.