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Message-ID: <m2sjmj572m.fsf@firstfloor.org> Date: Sun, 23 Oct 2011 21:47:45 -0700 From: Andi Kleen <andi@...stfloor.org> To: Eial Czerwacki <eial@...lemp.com> Cc: linux-kernel@...r.kernel.org, "Shai Fultheim \(Shai\@ScaleMP.com\)" <Shai@...lemp.com> Subject: Re: [PATCH] Move mostly read variables to __read_mostly section. Eial Czerwacki <eial@...lemp.com> writes: > * Once the number of bh's in the machine exceeds this level, we start > --- a/kernel/time/timekeeping.c 2010-05-12 14:59:32.000000000 -0700 > +++ b/kernel/time/timekeeping.c 2010-05-24 11:56:32.000000000 -0700 > @@ -154,7 +154,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOC > * used instead. > */ > static struct timespec xtime __attribute__ ((aligned (16))); > -static struct timespec wall_to_monotonic __attribute__ ((aligned (16))); > +static struct timespec wall_to_monotonic __attribute__ ((aligned > (16))) __read_mostly; That means that a common time fetch/update call will usually have to fetch two cachelines now instead of one, because it needs xtime and wall_to_monotonic. Usually those end up nearby. On the other hand it's rare to fetch wall_to_monotonic without xtime. So if anything all those variables should be grouped together in a single cacheline, but definitely not split like you do. The other changes in your patch are fine for me. -Andi -- ak@...ux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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