Date: Thu, 21 Oct 2010 16:53:30 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: David Wolfskill <david@catwhisker.org> Cc: performance@freebsd.org Subject: Re: Possible evidence of performance regression for 8.1-S (vs. 7.1) Message-ID: <20101021215330.GA86224@dan.emsphone.com> In-Reply-To: <20101020174854.GZ21226@albert.catwhisker.org> References: <20101020174854.GZ21226@albert.catwhisker.org>
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In the last episode (Oct 20), David Wolfskill said: > Almost 2 years ago, we migrated from a lightly-patched 6.2-R to 7.1-R with > 5 commits that were made to 7.1-S backported to it. On the same hardware > (not the HP mentioned above), I measured a 35% reduction in elapsed time > for one particular form of the build in question. This was encouraging. > > A couple of days ago, I updated the active slice on my 8.x reference > machine to 8.1-STABLE #5 r214029 and proceeded to start some timed builds; > here are some fairly raw timing data: > > Start Stop real user sys OS > 1287436357 1287461948 25590.99 81502.22 18115.07 8.1-S > 1287462797 1287488766 25969.26 81452.14 17920.14 8.1-S > 1287489641 1287515287 25645.84 81548.40 18256.52 8.1-S > 1287516151 1287541481 25329.64 81546.23 18294.10 8.1-S > 1287542355 1287568599 26244.59 81431.47 17902.39 8.1-S > > 1287525363 1287546846 21483.13 82628.20 21703.09 7.1-R+ > 1287548005 1287569100 21094.63 82853.19 22185.02 7.1-R+ > 1287570300 1287591371 21071.33 82756.81 21943.22 7.1-R+ An observation: on 8.1, both user and sys times are less, but real time is higher. So 8.1 finished the build using less CPU, but spent more time waiting for something else. Disk? Network? I don't suppose the machines are low enough on RAM that you end up swapping at any point? Maybe there was a change to /usr/bin/make that is causing it to launch jobs slower? Julian's suggestion of booting the 8.1 kernel on the 7.1 OS will definitely narrow down the list of suspects. -- Dan Nelson dnelson@allantgroup.com
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