From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by wa-out-1112.google.com with SMTP id j37so419255waf.22 for ; Wed, 12 Nov 2008 22:13:49 -0800 (PST) Subject: Re: [PATCH 3/4] add ksm kernel shared memory driver From: Eric Rannaud In-Reply-To: <23027.1226443216@turing-police.cc.vt.edu> References: <1226409701-14831-1-git-send-email-ieidus@redhat.com> <1226409701-14831-2-git-send-email-ieidus@redhat.com> <1226409701-14831-3-git-send-email-ieidus@redhat.com> <1226409701-14831-4-git-send-email-ieidus@redhat.com> <20081111150345.7fff8ff2@bike.lwn.net> <23027.1226443216@turing-police.cc.vt.edu> Content-Type: text/plain Date: Wed, 12 Nov 2008 22:13:47 -0800 Message-Id: <1226556827.13670.54.camel@nc050> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Valdis.Kletnieks@vt.edu Cc: Jonathan Corbet , Izik Eidus , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, aarcange@redhat.com, chrisw@redhat.com, avi@redhat.com List-ID: On Tue, 2008-11-11 at 17:40 -0500, Valdis.Kletnieks@vt.edu wrote: > On Tue, 11 Nov 2008 15:03:45 MST, Jonathan Corbet said: > Seems reasonably sane to me - only doing the first 128 bytes rather than > a full 4K page is some 32 times faster. Yes, you'll have the *occasional* > case where two pages were identical for 128 bytes but then differed, which is > why there's buckets. But the vast majority of the time, at least one bit > will be different in the first part. In the same spirit, computing a CRC32 instead of a SHA1 would probably be faster as well (faster to compute, and faster to compare the digests). The increased rate of collision should be negligible. Also, the upcoming SSE4.2 (Core i7) has a CRC32 instruction. (Support is already in the kernel: arch/x86/crypto/crc32c-intel.c) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org