Messages in this thread | | | Subject | Re: [Lse-tech] Re: [Patch 2/7] Add sysctl for schedstats | From | chandra seetharaman <> | Date | Mon, 27 Feb 2006 17:42:37 -0800 |
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On Tue, 2006-02-28 at 11:25 +1100, Nick Piggin wrote: > Chandra Seetharaman wrote: > > >On Mon, 2006-02-27 at 20:17 +1100, Nick Piggin wrote: > > > >>> #ifdef CONFIG_SCHEDSTATS > >>>+ > >>>+int schedstats_sysctl = 0; /* schedstats turned off by default */ > >>> > >>Should be read mostly. > >> > >> > >>>+static DEFINE_PER_CPU(int, schedstats) = 0; > >>>+ > >>> > >>When the above is in the read mostly section, you won't need this at all. > >> > >>You don't intend to switch the sysctl with great frequency, do you? > >> > > > >No, it is not expected to switch often. > > > >We originally coded it as __read_mostly, but thought the variable > >bouncing between CPUs would be costly. Is it cheaper with > >__read_mostly ? or it doesn't matter ? > > > > > > Well it will only "bounce" when the cacheline it is in is written to by > a different CPU. Considering this happens with your per-cpu implementation > _anyway_, they don't buy you anything much. > > Putting it in __read_mostly means that you won't happen to share a cacheline > with a variable that is being written to frequently. > Thanks for the clarification Nick.
> Nick > > -- > > Send instant messages to your online friends http://au.messenger.yahoo.com > > > > ------------------------------------------------------- > This SF.Net email is sponsored by xPML, a groundbreaking scripting language > that extends applications into web and mobile media. Attend the live webcast > and join the prime developer group breaking into this new coding territory! > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 > _______________________________________________ > Lse-tech mailing list > Lse-tech@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lse-tech
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