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Re: [Qemu-devel] QEMU/KVM performance gets worser - high load - high int


From: Gerhard Wiesinger
Subject: Re: [Qemu-devel] QEMU/KVM performance gets worser - high load - high interrupts - high context switches
Date: Fri, 11 Dec 2015 09:03:04 +0100
User-agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0

Any comments?

Ciao,
Gerhard

On 08.12.2015 10:39, Gerhard Wiesinger wrote:
Hello,

Yesterday I looked at my munin statistics on my KVM host and I swar that performance gets worser: load is getting higher, interrupts are getting higher and are high as well as context switches. VMs and applications didn't change that way.

You can find graphics at: http://www.wiesinger.com/tmp/kvm/
Last spike I guess was upgrade from FC22 to FC23 or a kernel update. And it was even lower on older versions

For me it looks like the high interrupt load and context switches are the root cause. Interrupts inside the VM are <100, so with 10 VMs I'm expecting 1000+baseload => <2000, see statistics below.

All VMs are virtio on disk/network except one (IDE/rtl8139).

# Host as well as all guests (except 2 VMs):
uname -a
Linux kvm 4.2.6-301.fc23.x86_64 #1 SMP Fri Nov 20 22:22:41 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

qemu-system-x86-2.4.1-1.fc23.x86_64

Platform:

All VMs have the pc-i440fx-2.4 profile (I upgraded yesterday from pc-i440fx-2.3 without any change).

Any ideas, anyone having same issues?

Ciao,
Gerhard

kvm: no VM running
r b swpd free buff cache si so bi bo in cs us sy id wa st 0 0 0 3308516 102408 3798568 0 0 0 12 197 679 0 0 99 0 0 0 0 0 3308516 102416 3798564 0 0 0 42 197 914 0 0 99 1 0 0 0 0 3308516 102416 3798568 0 0 0 0 190 791 0 0 100 0 0 2 0 0 3308484 102416 3798568 0 0 0 0 129 440 0 0 100 0 0

kvm: 2 VMs running
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 2641464 103052 3814700 0 0 0 0 2715 5648 3 2 95 0 0 0 0 0 2641340 103052 3814700 0 0 0 0 2601 5555 1 2 97 0 0 1 0 0 2641308 103052 3814700 0 0 0 5 2687 5708 3 2 95 0 0 0 0 0 2640620 103060 3814628 0 0 0 30 2779 5756 4 3 93 1 0 0 0 0 2640644 103060 3814636 0 0 0 0 2436 5364 1 2 97 0 0 1 0 0 2640520 103060 3814636 0 0 0 119 2734 5975 3 2 95 0 0

kvm: all 10 VMs running
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 60408 78892 3371984 0 0 0 85 9015 17357 4 9 87 0 0 2 0 0 60408 78892 3371968 0 0 0 47 9375 17797 9 9 82 0 0 0 0 0 60472 78892 3372092 0 0 40 60 8882 17343 4 8 86 1 0 1 0 0 60316 78892 3372080 0 0 0 59 8863 17517 4 8 87 0 0 0 0 0 59540 78900 3372092 0 0 0 55 9135 17796 8 9 81 1 0 0 0 0 59168 78900 3372112 0 0 0 51 8931 17484 4 9 87 0 0

cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 Quad CPU           @ 2.66GHz
stepping        : 7






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