Messages in this thread | | | From | "Vincent Sweeney" <> | Subject | Re: PROBLEM: high system usage / poor SMP network performance | Date | Tue, 29 Jan 2002 20:09:40 -0000 |
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----- 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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