Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to3.6-rc5 on AMD chipsets - bisected

From: Borislav Petkov
Date: Fri Sep 14 2012 - 17:45:28 EST

On Fri, Sep 14, 2012 at 11:40:43PM +0200, Peter Zijlstra wrote:
> Hmm, cute. What kind of machine did you test it on? Nikolay's machines
> look to be smallish AMD X6 or ancient Intel c2d (the patch will indeed
> have absolutely no effect on a dual core).

Yep, I took an X6 too. So it's a single-socket, 6-core AMD, F10h.

> I'll see about running pgbench on a bigger Intel tomorrow if Mike
> doesn't beat me to it.

Can try that too on one of the bigger machines I have, if needed.

> The problem the patch is trying to address is not having to scan an
> entire package for idle cores on every wakeup now that packages are
> getting stupid big.
> Regressing Postgres otoh isn't nice either..
> Anyway, I guess I'm fine with nixing this patch until we figure out
> something smarter..
> I'm also curious to know wth postgres does that this patch makes such a
> big difference...

I'm using 9.1 in Debian testing while Nikolay is using 9.2.


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