Messages in this thread | | | Date | Mon, 27 Feb 2012 08:40:50 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs |
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* Jason Baron <jbaron@redhat.com> wrote:
> On Fri, Feb 24, 2012 at 10:08:11AM +0100, Ingo Molnar wrote: > > * Jason Baron <jbaron@redhat.com> wrote: > > > > > 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)', [...] > > > > Yeah, there is such an overlap - I've renamed it to > > static_key_enabled(), which makes sense anyway as the original > > was jump_label_enabled().. > > > > Btw., shouldnt it be an inline function? Currently it's: > > > > Yes. I've had thought that too. In fact, it is already 'static > inline' for the !JUMP_LABEL case. So we can probably just > remove the function from the .c and move the 'static inline' > such that its defined for all cases.
Yep. Mind sending a patch for that, against latest -tip?
Thanks,
Ingo
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