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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