Thread (19 messages) 19 messages, 4 authors, 2010-03-19

Re: [PATCH 6/6] powerpc: Use lwsync for acquire barrier if CPU supports it

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2010-02-16 04:19:11

On Mon, 2010-02-15 at 22:22 -0600, Olof Johansson wrote:
Turns out this one hurts PA6T performance quite a bit, lwsync seems to be
significantly more expensive there. I see a 25% drop in the microbenchmark
doing pthread_lock/unlock loops on two cpus.

Taking out the CPU_FTR_LWSYNC will solve it, it's a bit unfortunate since
the sync->lwsync changes definitely still can, and should, be done. 
So we should use a different feature bit. No biggie. If needed we can
split them more anyways.

Cheers,
Ben.
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