Messages in this thread | | | Date | Tue, 24 Apr 2012 16:45:14 -0700 | From | Josh Triplett <> | Subject | Re: [RFC/PATCH] Prevent wasting time to find out get_parent_ip |
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On Wed, Apr 25, 2012 at 08:31:24AM +0900, Minho Ban wrote: > On 04/24/2012 09:53 PM, Peter Zijlstra wrote: > > On Tue, 2012-04-24 at 21:36 +0900, Minho Ban wrote: > >> trace_preempt_on/off looks empty if PREEMPT_TRACER is off. But actually it is > >> spending time to find out get_parent_ip(even CALLER_ADDR for some ARCH) which is > >> in argument. This seems not fair for those who expect to do nothing but increase > >> or decrease count. > > > > You can do the same by making them CPP macros and adding a comment as to > > why they're macros instead of inlines.. > > > > Thank you for pointing this out, certainly macros look better. I'll amend this.
As an alternative, how about making get_parent_ip and its called functions static inlines? Then the compiler can eliminate them via dead code elimination.
Or, how about declaring get_parent_ip with the GCC "pure" attribute? That would tell GCC that it can safely eliminate calls to the function.
- Josh Triplett
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