Messages in this thread | | | Date | Thu, 23 Feb 2012 21:25:13 -0500 | From | Jason Baron <> | Subject | Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs |
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On Thu, Feb 23, 2012 at 06:18:42PM -0500, Mathieu Desnoyers wrote: > * Ingo Molnar (mingo@elte.hu) wrote: > > > > * Ingo Molnar <mingo@elte.hu> wrote: > > > > > So, a modified scheme would be: > > > > > > #include <linux/static_key.h> > > > > > > struct static_key key = STATIC_KEY_INIT_TRUE; > > > > > > if (static_key_false(&key)) > > > do unlikely code > > > else > > > do likely code > > > > > > Or: > > > > > > if (static_key_true(&key)) > > > do likely code > > > else > > > do unlikely code > > > > > > The static key is modified via: > > > > > > static_key_slow_inc(&key); > > > ... > > > static_key_slow_dec(&key); > > > > > > Is that API fine? I'll rework the series to such an effect if > > > everyone agrees. > > > > I.e. something like the patch below on top of > > tip:perf/jump-labels. > > > > Untested - will test it and will refactor the series if > > everyone's happy. > > Hi Ingo, > > Reading your documentation updates makes me realise that adding the > "inline" keyword in there would make the whole thing even clearer: > > struct static_key key = STATIC_KEY_INLINE_TRUE_INIT; > struct static_key key = STATIC_KEY_INLINE_FALSE_INIT; > > static_key_inline_true() / static_key_inline_false() > > to show that the "true/false" in there does not mean that the key will > always be true or false (the key value can indeed by changed by calling > static_key_slow_inc/dec), but that the inlined path is either the true > of false branch. >
Also, as part of the API, there is a test to check the branch direction - which was 'jump_label_true(key)', but is now also 'static_key_true(key)', so we are going to have to change either the branch site or the test for true/false name. The above 'static_key_inline_true/false' solves that.
Also, I do like having a consistent 'static_key_*' prefix for the entire API - definitely an improvement for me.
Thanks,
-Jason
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