----- Original Message -----
From: "Dan Kegel" <dank@kegel.com>
To: "Vincent Sweeney" <v.sweeney@barrysworld.com>;
<linux-kernel@vger.kernel.org>
Sent: Tuesday, January 29, 2002 6:00 PM
Subject: Re: PROBLEM: high system usage / poor SMP network performance
> "Vincent Sweeney" <v.sweeney@barrysworld.com> wrote:
> > > > > CPU0 states: 27.2% user, 62.4% system, 0.0% nice, 9.2% idle
> > > > > CPU1 states: 28.4% user, 62.3% system, 0.0% nice, 8.1% idle
> > > >
> > > > The important bit here is ^^^^^^^^ that one. Something is
causing
> > > > horrendous lock contention it appears.
> > ...
> > Right then, here is the results from today so far (snapshot taken with
2000
> > users per ircd). Kernel profiling enabled with the eepro100 driver
compiled
> > statically.
> > readprofile -r ; sleep 60; readprofile | sort -n | tail -30
> > ...
> > 170 sys_poll 0.1897
> > 269 do_pollfd 1.4944
> > 462 remove_wait_queue 12.8333
> > 474 add_wait_queue 9.1154
> > 782 fput 3.3707
> > 1216 default_idle 23.3846
> > 1334 fget 16.6750
> > 1347 sock_poll 33.6750
> > 2408 tcp_poll 6.9195
> > 9366 total 0.0094
> > ...
> > So with my little knowledge of what this means I would say this is
purely
> > down to poll(), but surely even with 4000 connections to the box that
> > shouldn't stretch a dual P3-800 box as much as it does?
>
> My oldish results,
> http://www.kegel.com/dkftpbench/Poller_bench.html#results
> show that yes, 4000 connections can really hurt a Linux program
> that uses poll(). It is very tempting to port ircd to use
> the Poller library
(http://www.kegel.com/dkftpbench/dkftpbench-0.38.tar.gz);
> that would let us compare poll(), realtimesignals, and /dev/epoll
> to see how well they do on your workload.
> - Dan
>
So basically you are telling me these are my options:
1) Someone is going to have to recode the ircd source we use and
possibly a modified kernel in the *hope* that performance improves.
2) Convert the box to FreeBSD which seems to have a better poll()
implementation, and where I could support 8K clients easily as other admins
on my chat network do already.
3) Move the ircd processes to some 400Mhz Ultra 5's running Solaris-8
which run 3-4K users at 60% cpu!
Now I want to run Linux but unless I get this issue resolved I'm essentialy
not utilizing my hardware to the best of its ability.
Vince.
-
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This archive was generated by hypermail 2b29 : Thu Jan 31 2002 - 21:01:24 EST