Messages in this thread | | | From | "Vincent Sweeney" <> | Subject | PROBLEM: high system usage / poor SMP network performance | Date | Sun, 27 Jan 2002 22:23:17 -0000 |
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I am the server admin for several very busy IRC servers with an ever increasing user load but I've hit a severe bottle neck which after numerous system tweaks and driver configuration changes I can only assume is related to a performance problem with the Linux Kernel.
The server configurations are all identical: Compaq Proliant 330R's with Dual Pentium III -800 MHz's & 384MB RAM Intel NIC's using the Intel e100 driver 2.4.17 kernel 2 ircd processes per box
Here is a snapshot from 'top' : 9:51pm up 11 days, 10:13, 1 user, load average: 0.95, 1.24, 1.21 44 processes: 40 sleeping, 4 running, 0 zombie, 0 stopped 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 Mem: 385096K av, 376896K used, 8200K free, 0K shrd, 3588K buff Swap: 379416K av, 12744K used, 366672K free 58980K cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND 7825 ircd 18 0 84504 82M 5604 R 89.5 21.9 6929m ircd 31010 ircd 20 0 86352 84M 5676 R 85.0 22.3 7218m ircd
When this snapshot was taken each ircd had 2000 users connect each. As you can see I am using more than a single cpu's worth of processer power just on system cpu and the ircd processes are using just over 50% of a single cpu! Now in comparison, another server admin who runs a ircd on a single P3-500 Linux 2.4.x system with 3000 users reaches about 60% *total* cpu usage. Likewise admins who run *BSD or Solaris can run with similar user connections and barely break a sweat. I have tried setting all the network performance tweaks mentioned on numerous sites and also using the cpu saver option on the e100 driver but at best I have only seen a 1-2% cpu saving.
Naturally I would really like to know where / what is using up all this system cpu so I would like to try profiling the kernel as I'm sure this is a pure kernel network layer performance issue but I have no idea where to start so does anyone have some advice / tips on where I should start?
Vince.
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