Date: Wed, 20 Jun 2007 12:17:52 -0400 (EDT) From: David Cross <dcross@okcupid.com> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-hackers@freebsd.org Subject: Re: Very slow sed... Message-ID: <20070620121351.W56928@max.okcupid.com> In-Reply-To: <20070620160916.GA26574@rot26.obsecurity.org> References: <20070620100737.S56928@max.okcupid.com> <20070620160916.GA26574@rot26.obsecurity.org>
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On Wed, 20 Jun 2007, Kris Kennaway wrote: > On Wed, Jun 20, 2007 at 10:24:01AM -0400, David Cross wrote: > >> Machine 2: >> time sed -f >> /usr/src/gnu/usr.bin/groff/tmac/../../../../contrib/groff/tmac/strip.sed >> /usr/src/gnu/usr.bin/groff/tmac/../../../../contrib/groff/tmac/doc-common >>> /dev/null >> >> real 0m4.506s >> user 0m4.167s >> sys 0m0.000s >> >> Yes... you read that right... almost 400 _TIMES_ slower. WTF.. >> >> Where should I be looking? > > Try ktracing to see what it is doing (although sys time = 0 says it's > all in userland). So maybe gprof or pmc. Also double check the > kernel configs are identical and malloc debugging is disabled. I ktraced it, its basically just writing data, averaging about 20 bytes per write (that's how I came up with the bs= number on the dd line, trying to simulate it. I agree that it _SEEMS_ to be userland, BUT what I am suspecting is that the slowdown is in the transition between kernel and userland, but I am unsure how to check this. Kernel config is "SMP" on both. I will note its also more then just sed, the whole machine FEELs sluggish, that's just the clearest example I could show. -- David E. Cross That being said, dd SHOULD have the same problem. I will work on gprof-ing it now. > > Kris >
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