Messages in this thread | | | Date | Fri, 26 Jul 2002 12:56:05 +0530 | From | Kiran <> | Subject | Re: Patch 2.5.25: Ensure xtime_lock and timerlist_lock are on difft cachelines |
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On Fri, Jul 26, 2002 at 04:24:51PM +1000, Rusty Russell wrote: > In message <20020725204512.E3594@in.ibm.com> you write: > > I've noticed that xtime_lock and timerlist_lock ends up on the same > > cacheline all the time (atleaset on x86). Not a good thing for > > loads with high xxx_timer and do_gettimeofday counts I guess (networking etc) > .. > > Better might be to use the x86-64 trick of using sequence counters > around do_gettimeofday, and avoid the xtime lock altogether. That > will improve gettimeofday performance as well. Or you could try > changing xtime lock to a brlock. >
Ok, I'll look at the x86-64 code
> FYI: as policy, I don't take optimization patches without > measurements. I'm just not that smart. >
This patch was not meant to be a definitive fix for do_gettimeofday. I thought having diffrent locks on the same cacheline was bad. Atleast, I don't think there'd be any negative performance impact due to my patch. Pls correct me if I am wrong.
I want to get some nos too .. and probably will...(still waiting for my turn to use the 4way here :-) ). But, I decided to post this patch as a follow up to the 2.5 profiler discussion on lse-tech. Anywayz, point taken. Next time I submit an optimization patch to you, I'll post the measuements too.
Thanks, Kiran
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