Messages in this thread | | | Date | Tue, 24 Jul 2007 15:22:56 -0400 | From | Chris Snook <> | Subject | Re: miserable performance of 2.6.21 under network load |
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Aaron Porter wrote: > On Tue, Jul 24, 2007 at 08:48:00PM +0200, Andi Kleen wrote: >> Aaron Porter <atporter@primate.net> writes: >> >>> 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. >> Can you oprofile it? > > # opreport -l > CPU: AMD64 processors, speed 1994.52 MHz (estimated) > Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit mask of 0x00 (No unit mask) count 100000 > samples % app name symbol name > 914379 48.8404 vmlinux-2.6.21.5 check_poison_obj > 341920 18.2632 vmlinux-2.6.21.5 poison_obj
I bet you have CONFIG_DEBUG_SLAB turned off in your 2.6.17 kernel, and turned on in your 2.6.21 kernel.
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