Messages in this thread | | | Subject | Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected | From | Peter Zijlstra <> | Date | Fri, 14 Sep 2012 23:59:31 +0200 |
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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.
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.
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