From: "Darrick J. Wong" Subject: Re: [PATCH 14/14] crc32: Select an algorithm via kconfig Date: Tue, 13 Dec 2011 10:36:44 -0800 Message-ID: <20111213183644.GO7137@tux1.beaverton.ibm.com> References: <20111201201341.5876.83743.stgit@elm3c44.beaverton.ibm.com> <20111201201517.5876.39207.stgit@elm3c44.beaverton.ibm.com> <20111202002505.GB19842@gondor.apana.org.au> <20111203023646.GB16577@tux1.beaverton.ibm.com> <20111212225857.GM7137@tux1.beaverton.ibm.com> <02ea01ccb923$48193ff0$d84bbfd0$@systemfabricworks.com> <20111213063228.GN7137@tux1.beaverton.ibm.com> Reply-To: djwong@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "'Andreas Dilger'" , "'Andrew Morton'" , "'Mingming Cao'" , "'Herbert Xu'" , "'linux-crypto'" , linux-ext4@vger.kernel.org, "'linux-fsdevel'" , "'linux-kernel'" , Bob Pearson , "'Theodore Tso'" To: Joakim Tjernlund Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue, Dec 13, 2011 at 09:27:10AM +0100, Joakim Tjernlund wrote: > "Darrick J. Wong" wrote on 2011/12/13 07:32:28: > > > > On Mon, Dec 12, 2011 at 05:10:45PM -0600, Bob Pearson wrote: > > > That choice was for Joakim who measured better performance on his 32 bit PPC > > > platform with "by 4". > > > > Ok. On my 1.33GHz PowerBook I get ~255MB/s with slice by 4 and ~270MB/s with > > slice by 8. I think it's a PPC 7447, and definitely 32-bit. In any case, it > > reports having 32K of L1D cache. > > I tested Bobs early version on my mpc8321(266MHz, embedded CPU) and it was just > half the speed compared with current crc32. I wonder, given the patch "crc32: Speed up memory table access on powerpc" would you mind retesting to see if slice by 8 still trails slice by 4 on your powerpc? I see that your mpc8321 has 16K of L1D cache and a 32-bit memory bus whereas my 7447 has a 64-bit memory bus. I wonder if memory bus size could be a defining characteristic...? I tried it out the crc32c code on a s390x today; apparently by-8 trails by-4 there too. It's unfortunately difficult to figure out the hardware details of whatever's going on underneath that VM. --D > > Jocke > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >