Re: %cpu in system - squid performance in FreeBSD 5.3

From: Darcy Buskermolen (darcy_at_wavefire.com)
Date: 01/04/05

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    To: freebsd-net@freebsd.org
Date: Tue, 4 Jan 2005 14:22:29 -0800

    On January 4, 2005 11:18 am, Sean Chittenden wrote:
    > > PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU CPU
    > > COMMAND
    > > 474 squid 96 0 68276K 62480K select 0 53:38 16.80% 16.80%
    > > squid
    > > 311 bind 20 0 10628K 6016K kserel 0 12:28 0.00% 0.00%
    > > named
    > >
    > > It's actually so good that one machine can now handle all traffic
    > > (around 180 Mb/s) at < %50 cpu utilization. Seems like something in
    > > the
    > > network stack is responsible for the high %system cpu util...
    >
    > OH!!!! Wow, I should've noticed that earlier. Your hint about someone
    > on Linux having the same problem tipped me off to look at the process
    > state again. Anyway, you nearly answered your own question, save you
    > probably aren't familiar with select(2)'s lack of scalability. Read
    > these:
    >
    > http://www.kegel.com/c10k.html
    >
    >
    > Specifically the four methods mentioned here:
    >
    > http://www.kegel.com/c10k.html#nb.select
    >
    >
    > Then look at the benchmarks done using libevent(3):
    >
    > http://www.monkey.org/~provos/libevent/
    >
    >
    > Dime to dollar you're spending all of your time copying file descriptor
    > arrays in and out of the kernel because squid uses select(2) instead of
    > kqueue(2). Might be an interesting project for someone to take up to
    > convert that to kqueue(2). Until then, any local TCP load balancer
    > that uses kqueue(2) would also solve your problem (I'm not aware of any
    > off the top of my head... pound(8) does, but it is only used for HTTP
    > and is not a reverse proxy) and would likely prevent you from having
    > your problems. -sc

    squid-dev has kqueue support already.

    ./configure --disable-select --disable-poll --enable-kqueue 

    -- 
Darcy Buskermolen
Wavefire Technologies Corp.
ph: 250.717.0200
fx:  250.763.1759
http://www.wavefire.com
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