Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 24 Sep 2012 09:33:20 -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 Mon, Sep 24, 2012 at 9:07 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > On Mon, 2012-09-24 at 08:52 -0700, Linus Torvalds wrote: >> Your patch looks odd, though. Why do you use some complex initial >> value for 'candidate' (nr_cpu_ids) instead of a simple and readable >> one (-1)? > > nr_cpu_ids is the typical no-value value for cpumask operations -- yes > this is annoying and I keep doing it wrong far too often.
Can we please just fix it? Making the excuse that it's the "typical no-value" is still stupid, because it's a f*cking moronic no-value.
Whoever thinks that it's smart to test against "nr_cpu_ids" when there's a much more natural value (-1) is crazy. The source code looks more complex, but the code it *generates* is clearly more complex and worse too.
Sure, the "scan bits" bitops will return ">= nr_cpu_ids" for the "I couldn't find a bit" thing, but that doesn't mean that everything else should.
Linus
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