From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Kukunas Subject: Re: RAID5 XOR speed vs RAID6 Q speed (was Re: AVX RAID5 xor checksumming) Date: Mon, 2 Apr 2012 15:48:18 -0700 Message-ID: <20120402224818.GA2248@jtkukuna_gentoo_sb> References: <1333057458-2986-1-git-send-email-james.t.kukunas@linux.intel.com> <4F76ECD0.1060608@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4F76ECD0.1060608@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sat, Mar 31, 2012 at 12:38:56PM +0100, John Robinson wrote: > On 29/03/2012 22:44, Jim Kukunas wrote: > > Based on xor_speed, the AVX implementation appears to be ~32% faster than the > > SSE implementation on my i7 2600: > > > > generic_sse: 15088.000 MB/sec > > avx: 19936.000 MB/sec > > I just noticed in my logs the other day (recent el5 kernel on a Core 2): > > raid5: automatically using best checksumming function: generic_sse > generic_sse: 7805.000 MB/sec > raid5: using function: generic_sse (7805.000 MB/sec) > raid6: int64x1 2635 MB/s > raid6: int64x2 3208 MB/s > raid6: int64x4 3020 MB/s > raid6: int64x8 2519 MB/s > raid6: sse2x1 5099 MB/s > raid6: sse2x2 5742 MB/s > raid6: sse2x4 8237 MB/s > raid6: using algorithm sse2x4 (8237 MB/s) > > I was just wondering how it's possible to do the RAID6 Q calculation > faster than the RAID5 XOR calculation - or am I reading this log excerpt > wrongly? Out of curiosity, are you running with CONFIG_PREEMPT=y? Thanks. > > It's probably academic, since the machine this is running on only has a > maximum of about 4500 MB/s of memory throughput, and a lot of that would > be consumed sending data to disc in amongst the calculations being done. > > Cheers, > > John. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jim Kukunas Intel Open Source Technology Center