On Thu, Oct 23, 2008 at 03:43:58PM +1100, Benjamin Herrenschmidt wrote: > On Wed, 2008-10-22 at 17:59 +0200, Ingo Molnar wrote: > > * Nick Piggin <npiggin@xxxxxxx> wrote: > > > > > Speed up generic mutex implementations. > > > > > > - atomic operations which both modify the variable and return something imply > > > full smp memory barriers before and after the memory operations involved > > > (failing atomic_cmpxchg, atomic_add_unless, etc don't imply a barrier because > > > they don't modify the target). See Documentation/atomic_ops.txt. > > > So remove extra barriers and branches. > > > > > > - All architectures support atomic_cmpxchg. This has no relation to > > > __HAVE_ARCH_CMPXCHG. We can just take the atomic_cmpxchg path unconditionally > > > > > > This reduces a simple single threaded fastpath lock+unlock test from 590 cycles > > > to 203 cycles on a ppc970 system. > > > > > > Signed-off-by: Nick Piggin <npiggin@xxxxxxx> > > > > no objections here. Lets merge these two patches via the ppc tree, so > > that it gets testing on real hardware as well? > > > > Acked-by: Ingo Molnar <mingo@xxxxxxx> > > Allright but in that case it will be after -rc1 unless I manage to sneak > something in tomorrow before linux closes the merge window. > > I can't get an update today. Fine with me. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
