From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Avi Kivity <avi@redhat.com>, Ryan Harper <ryanh@us.ibm.com>,
Anthony Liguori <aliguori@linux.vnet.ibm.com>,
bharata@in.ibm.com,
"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
Balbir Singh <balbir@in.ibm.com>,
kmr@us.ibm.com
Subject: Effect of nice value on idle vcpu threads consumption
Date: Sat, 19 Feb 2011 17:12:48 +0530 [thread overview]
Message-ID: <20110219114248.GA19999@linux.vnet.ibm.com> (raw)
Hello,
I have been experimenting with renicing vcpu threads and found some
oddity. I was expecting a idle vcpu thread to consume close to 0% cpu resource
irrespective of its nice value. That was true when nice value was 0 for vcpu
threads. However altering nice value of (idle) vcpu threads is causing its cpu
consumption to shoot up. Does anyone have a quick answer to this behavior?
More details.
Machine : x3650-M2 w/ 2 Quad-core CPUs (Intel Xeon X5570), HT enabled
Host : RHEL 6 distro w/ 2.6.38-rc5 kernel
Single Guest : w/ 4vcpus (all vcpus pinned to physical cpu 0), 1GB mem
Sles11 distro w/ 2.6.37 kernel
Single guest is booted and kept idle.
When all vcpu threads are at nice 0, here's the consumption (close to 0 for all
vcpu threads).
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
5642 qemu 20 0 1567m 381m 3048 S 1.2 1.2 0:02.56 0 qemu-kvm
5640 qemu 20 0 1567m 381m 3048 S 0.8 1.2 0:12.74 0 qemu-kvm
5641 qemu 20 0 1567m 381m 3048 S 0.8 1.2 0:02.60 0 qemu-kvm
5643 qemu 20 0 1567m 381m 3048 S 0.6 1.2 0:02.76 0 qemu-kvm
Changing nice value for one of the vcpu threads to -20:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
5640 qemu 0 -20 1567m 381m 3048 R 45.5 1.2 0:19.67 0 qemu-kvm
5641 qemu 20 0 1567m 381m 3048 R 0.4 1.2 0:03.33 0 qemu-kvm
5642 qemu 20 0 1567m 381m 3048 R 0.4 1.2 0:03.16 0 qemu-kvm
5643 qemu 20 0 1567m 381m 3048 R 0.4 1.2 0:03.36 0 qemu-kvm
Changing nice value for another of the vcpu threads to -20:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
5640 qemu 0 -20 1567m 381m 3048 S 35.7 1.2 0:30.92 0 qemu-kvm
5641 qemu 0 -20 1567m 381m 3048 S 26.1 1.2 0:04.77 0 qemu-kvm
5642 qemu 20 0 1567m 381m 3048 S 0.2 1.2 0:03.29 0 qemu-kvm
5643 qemu 20 0 1567m 381m 3048 S 0.2 1.2 0:03.50 0 qemu-kvm
Is this behavior expected? Any explanation for this behavior?
- vatsa
reply other threads:[~2011-02-19 11:42 UTC|newest]
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