Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 14 Sep 2012 15:01:44 -0700 | Subject | Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected |
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On Fri, Sep 14, 2012 at 2:56 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > Both things change semantics, not looking at the entire package is new > too.
Well, the "idle_buddy" thing on its own could be considered to be purely a caching thing.
Sure, it doesn't take tsk_cpus_allowed() into account while setting up the cache (since it's not dynamic enough), but *assuming* the common case is that people let threads be on any of the cores of a package, it should be possible to make the cache 100% equivalent with no semantic change. No?
The code doesn't even try to do that kind of "don't change semantics", though, and makes the idle-buddy thing entirely different.
Linus
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