From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id C27EAB7D06 for ; Tue, 16 Feb 2010 15:19:11 +1100 (EST) Subject: Re: [PATCH 6/6] powerpc: Use lwsync for acquire barrier if CPU supports it From: Benjamin Herrenschmidt To: Olof Johansson In-Reply-To: <20100216042238.GB12167@lixom.net> References: <20100210105728.GA3399@kryten> <20100210110236.GB3399@kryten> <20100210110306.GC3399@kryten> <20100210110406.GD3399@kryten> <20100210110719.GE3399@kryten> <20100210111025.GF3399@kryten> <20100216042238.GB12167@lixom.net> Content-Type: text/plain; charset="UTF-8" Date: Tue, 16 Feb 2010 15:19:03 +1100 Message-ID: <1266293943.16346.169.camel@pasglop> Mime-Version: 1.0 Cc: npiggin@suse.de, linuxppc-dev@ozlabs.org, Anton Blanchard List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.