Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752363Ab2HUGio (ORCPT ); Tue, 21 Aug 2012 02:38:44 -0400 Received: from isrv.corpit.ru ([86.62.121.231]:51372 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750918Ab2HUGim (ORCPT ); Tue, 21 Aug 2012 02:38:42 -0400 Message-ID: <50332CEF.7010204@msgid.tls.msk.ru> Date: Tue, 21 Aug 2012 10:38:39 +0400 From: Michael Tokarev Organization: Telecom Service, JSC User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:10.0.5) Gecko/20120624 Icedove/10.0.5 MIME-Version: 1.0 To: Will Drewry CC: Stephen Warren , Tejun Heo , "linux-kernel@vger.kernel.org" , "cross-distro@lists.linaro.org" , Jens Axboe , Kay Sievers Subject: Re: root=PARTUUID for MBR/NT disk signatures? References: <502EC16C.4030007@wwwdotorg.org> <20120820182254.GQ24861@google.com> <50328258.9030800@wwwdotorg.org> In-Reply-To: X-Enigmail-Version: 1.4.1 OpenPGP: id=804465C5 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1080 Lines: 24 On 21.08.2012 08:47, Will Drewry wrote: [] > Functionally, I suspect this will work fine, but I am concerned that > it is a bad move from an efficiency perspective (not unfixable > though). Right now, the user-supplied value is converted from > string-uuid to packed-uuid. This is then memcmp'd across any and all > partitions - be it 2 or 200 - across all attached storage. If we move > to a pure string, then we end up needing to unpack every packed UUID > at disk scan time (or search, depending on impl) rather than just the > one user supplied value. > > Perhaps the cost is negligible on modern machines, but it seems like > the wrong place to put the cost (per entry rather than per search > value). Amount of work needed to READ all the partition tables might be quite a bit larger than strcmp'ing it all. I think. /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/