Messages in this thread |  | | | Date | Tue, 6 Jan 2009 07:55:58 -0800 (PST) | | From | Linus Torvalds <> | | Subject | Re: [PATCH][RFC]: mutex: adaptive spin |
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On Tue, 6 Jan 2009, Ingo Molnar wrote: > > The thing i like most about Peter's patch (compared to most other adaptive > spinning approaches i've seen, which all sucked as they included various > ugly heuristics complicating the whole thing) is that it solves the "how > long should we spin" question elegantly: we spin until the owner runs on a > CPU.
The other way around, you mean: we spin until the owner is no longer holding a cpu.
I agree that it's better than the normal "spin for some random time" model, but I can't say I like the "return 0" cases where it just retries the whole loop if the semaphore was gotten by somebody else instead. Sounds like an easyish live-lock to me. I also still strongly suspect that whatever lock actually needs this, should be seriously re-thought.
But apart from the "return 0" craziness I at least dont' _hate_ this patch. Do we have numbers? Do we know which locks this matters on?
Linus
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