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
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.