Messages in this thread | | | Date | Tue, 24 Jul 2007 14:49:47 -0400 | From | Chris Snook <> | Subject | Re: miserable performance of 2.6.21 under network load |
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Aaron Porter wrote: > I'm in the process up upgrading a pool of apache servers from > 2.6.17.8 to 2.6.21.5, and we're seeing a pretty major change in behavior. > Under identical network load, 2.6.21 has a load average more than 3 times > higher, cpu 0 spends well over 90% of its time in interrupts (vs ~30% > under 2.6.17). When we hit 3k apache sessions, ksoftirqd eats 100% of cpu0 > and our network traffic drops off rapidly. The end result is that 2.6.17 > performs twice as well under this load.
Is it always CPU 0, or does it move? Are you running irqbalance? If you're running irqbalance, you can run a script that alternates between 'cat /proc/interrupts' and 'mpstat -P ALL 5 10' and watch the offending interrupt jump around between processors. It's not as informative as oprofile, as Andi suggested, but it's really easy to set up.
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