Date: Tue, 03 Jan 2012 02:37:34 -0500 From: "Dieter BSD" <dieterbsd@engineer.com> To: freebsd-performance@freebsd.org Subject: Re: cmp(1) has a bottleneck, but where? Message-ID: <20120103073736.218240@gmx.com>
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>>>> Task: cp(1) a several-GB file from one drive to another, >>>> then run cmp(1) to verify. Cp runs as expected, but >>>> cmp runs slower than expected. Neither the disks >>>> nor the cpu is maxed out. Local drives, no network >>>> involved. Machine is otherwise idle. >>> >>> 1. How are you running cmp? >>> 2. Why do you claim cmp is the bottleneck? Is it spinning the CPU? >> >> cmp big_file /other_disk/big_file >> >> Cmp is running slower than it should. It isn't cpu bound ( 67.5%Idle ) >> but it isn't disk bound either. Seems like it should be one or the >> other. > > What gets output on the console when you do CTRL-T? load: 0.59 cmd: cmp 93304 [vnread] 56.99r 8.50u 3.80s 23% 720k load: 0.59 cmd: cmp 93304 [vnread] 57.68r 8.60u 3.85s 22% 720k load: 0.54 cmd: cmp 93304 [vnread] 60.69r 9.03u 4.12s 22% 780k load: 0.54 cmd: cmp 93304 [runnable] 63.79r 9.58u 4.26s 22% 720k load: 0.58 cmd: cmp 93304 [runnable] 68.33r 10.28u 4.62s 21% 788k load: 0.53 cmd: cmp 93304 [runnable] 71.92r 10.78u 4.94s 23% 720k load: 0.53 cmd: cmp 93304 [vnread] 72.31r 10.84u 4.96s 21% 780k load: 0.44 cmd: cmp 93304 [vnread] 198.84r 30.64u 14.36s 23% 720k
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