lkml.org 
[lkml]   [2012]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected
From
Date
On Fri, 2012-09-14 at 23:59 +0200, Peter Zijlstra wrote: 
> On Fri, 2012-09-14 at 23:56 +0200, Peter Zijlstra wrote:
> > On Fri, 2012-09-14 at 14:44 -0700, Linus Torvalds wrote:
> > > On Fri, Sep 14, 2012 at 2:40 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > > >
> > > > 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.
> > >
> > > No, it does something *else* too. That whole "left-right" logic to
> > > (according to the commit message) "prevent bouncing" is entirely new,
> > > afaik.
> > >
> > > So it is *not* just about avoiding to have to scan the whole package.
> > > It changes actual semantics too. No?
> >
> > Both things change semantics, not looking at the entire package is new
> > too. But yeah I guess you could look at the exact cross-stitching as an
> > enhancement to the 'idle_buggy' thing.
>
> What I'm saying is that having an idle_buggy means you have to assign
> one in the first place, his left-right stuff might not be the simplest
> means to do that -- in fact I suggested he do a simple shift first time
> I saw that patch.

Shift just means that upon perturbation, tasks shift their way around
the package vs random bounce around, that's why I cross wired.
> So if not the left-right thing, you still need to do _something_ to make
> the idle_buggy work at all. So its not entirely separate.

Yeah.

-Mike




\
 
 \ /
  Last update: 2012-09-15 06:41    [W:0.147 / U:10.456 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site