On 12/13/2009 01:58 PM, Ozan Çağlayan wrote:
KVM related messages on the host server: ~ # dmesg |grep kvm [ 3649.058945] loaded kvm module (kvm-kmod-2.6.32) [ 3683.736737] kvm: emulating exchange as write (It's interesting, what does it mean?)
An exchange instruction (cmpxchg, likely) was emulated using a write. Since it happens under lock, this is safe.
First of all if there are some specific outputs that will reveal the IO/CPU boundness of the workload, I'd like to give them too. I'm not much familiar with diagnostic/analysis tools.. From host's POV: ---------------- Guest is idle: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 26117 root 20 0 2153m 175m 1356 S 5 0.5 0:33.57 qemu-kvm Guest is configuring CUPS: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 26117 root 20 0 2129m 180m 1356 S 143 0.6 0:44.34 qemu-kvm (peak at 140,150~ %CPU)
Definitely looks cpu bound.
load average reached 0.91 at the end of the configuration. SMP view of top command shows that only Cpu2 and Cpu9 are involved, other ones are zeroed (maybe coherent with -smp 2, don't have much idea): Cpu2 : 28.4%us, 31.4%sy, 0.0%ni, 40.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu9 : 27.7%us, 26.7%sy, 0.0%ni, 45.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Can you provide kvm_stat output while this happens?
Configuring CUPS: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 19258 root 20 0 3396 1656 1192 R 18 0.1 0:05.20 configure (Saw maximum 22 %CPU)
Do you have any idea what this configure does? If it is a very fork/exec intensive workload, you can expect some slowdown on older processors.
The following is the highest load average instant during configuration: top - 11:35:32 up 33 min, 3 users, load average: 0.56, 0.25, 0.15 Tasks: 99 total, 4 running, 95 sleeping, 0 stopped, 0 zombie Cpu0 : 4.7%us, 68.3%sy, 0.0%ni, 27.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 4.3%us, 66.3%sy, 0.0%ni, 29.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 2061660k total, 137564k used, 1924096k free, 58672k buffers Swap: 307192k total, 0k used, 307192k free, 49240k cached vmstat -n 1: ------------ (context switches and interrupts are much more higher during configuration than the idle state)
1 0 0 1924788 58592 49176 0 0 0 0 1413 401 2 33 65 0 0 (./configure) 1 0 0 1924092 58592 49072 0 0 0 4 2210 599 5 57 38 0 0 1 0 0 1924544 58592 49080 0 0 0 0 2131 349 5 51 45 0 0
That's consistent with a fork/exec load, though the numbers are not that high.
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