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DescriptionJulio Entrena Perez
2018-08-17 10:42:50 UTC
Description of problem:
pidstat reports the wrong CPU for a pinned qemu-kvm thread
Version-Release number of selected component (if applicable):
sysstat-10.1.5-13.el7.x86_64
How reproducible:
Always
Steps to Reproduce:
1. Create a virtual machine and pin a VCPU thread to a CPU.
2. Run a CPU intensive workload in the VM (e.g. "openssl speed")
3.
Actual results:
pidstat reports the wrong CPU for the pinned VCPU qemu-kvm thread
Expected results:
pidstat reports the correct CPU for the pinned VCPU qemu-kvm thread
Additional info:
Example: a single VCPU VM has its VCPU pinned to CPU 0 in the host using
- "0#1" for RHV CPU pinning topology
or
- libvirt:
<cputune>
<vcpupin vcpu='0' cpuset='1'/>
</cputune>
# virsh -r vcpuinfo rhel7a
VCPU: 0
CPU: 1
State: running
CPU time: 289.8s
CPU Affinity: -y
# virsh -r vcpupin rhel7a
VCPU: CPU Affinity
----------------------------------
0: 1
1: 0-1
2: 0-1
3: 0-1
Running "top -H" and adding the P (processor) column shows that the VCPU thread is running in physical CPU 1:
top - 16:11:31 up 16 days, 21:39, 1 user, load average: 1.08, 0.75, 0.39
Threads: 359 total, 3 running, 356 sleeping, 0 stopped, 0 zombie
%Cpu(s): 50.2 us, 0.2 sy, 0.0 ni, 49.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 7881488 total, 1840740 free, 1300100 used, 4740648 buff/cache
KiB Swap: 1023996 total, 1023996 free, 0 used. 6201844 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
19762 qemu 20 0 2796560 835020 13424 R 99.3 10.6 6:29.88 1 CPU 0/KVM
1833 root 20 0 1546680 45292 11412 S 0.3 0.6 29:46.39 0 python
Taskset confirms this thread is bound to CPU 1:
# taskset -p 19762
pid 19762's current affinity mask: 2
But pidstat insists on reporting the VCPU thread as running on CPU 0:
# pidstat -ut -p 19753
Linux 3.10.0-693.21.1.el7.x86_64 (rhevh3-375.usersys.redhat.com) 13/08/18 _x86_64_ (2 CPU)
16:06:18 UID TGID TID %usr %system %guest %CPU CPU Command
16:06:18 107 19753 - 100.00 0.00 100.00 0.01 0 qemu-kvm
16:06:18 107 - 19753 0.00 0.00 0.00 0.00 0 |__qemu-kvm
16:06:18 107 - 19757 0.00 0.00 0.00 0.00 0 |__qemu-kvm
16:06:18 107 - 19758 0.00 0.00 0.00 0.00 0 |__IO
16:06:18 107 - 19762 0.00 0.00 0.00 0.00 0 |__CPU
16:06:18 107 - 19765 0.00 0.00 0.00 0.00 0 |__SPICE
16:06:18 107 - 21882 0.00 0.00 0.00 0.00 0 |__worker
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2019:2299
Description of problem: pidstat reports the wrong CPU for a pinned qemu-kvm thread Version-Release number of selected component (if applicable): sysstat-10.1.5-13.el7.x86_64 How reproducible: Always Steps to Reproduce: 1. Create a virtual machine and pin a VCPU thread to a CPU. 2. Run a CPU intensive workload in the VM (e.g. "openssl speed") 3. Actual results: pidstat reports the wrong CPU for the pinned VCPU qemu-kvm thread Expected results: pidstat reports the correct CPU for the pinned VCPU qemu-kvm thread Additional info: Example: a single VCPU VM has its VCPU pinned to CPU 0 in the host using - "0#1" for RHV CPU pinning topology or - libvirt: <cputune> <vcpupin vcpu='0' cpuset='1'/> </cputune> # virsh -r vcpuinfo rhel7a VCPU: 0 CPU: 1 State: running CPU time: 289.8s CPU Affinity: -y # virsh -r vcpupin rhel7a VCPU: CPU Affinity ---------------------------------- 0: 1 1: 0-1 2: 0-1 3: 0-1 Running "top -H" and adding the P (processor) column shows that the VCPU thread is running in physical CPU 1: top - 16:11:31 up 16 days, 21:39, 1 user, load average: 1.08, 0.75, 0.39 Threads: 359 total, 3 running, 356 sleeping, 0 stopped, 0 zombie %Cpu(s): 50.2 us, 0.2 sy, 0.0 ni, 49.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 7881488 total, 1840740 free, 1300100 used, 4740648 buff/cache KiB Swap: 1023996 total, 1023996 free, 0 used. 6201844 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND 19762 qemu 20 0 2796560 835020 13424 R 99.3 10.6 6:29.88 1 CPU 0/KVM 1833 root 20 0 1546680 45292 11412 S 0.3 0.6 29:46.39 0 python Taskset confirms this thread is bound to CPU 1: # taskset -p 19762 pid 19762's current affinity mask: 2 But pidstat insists on reporting the VCPU thread as running on CPU 0: # pidstat -ut -p 19753 Linux 3.10.0-693.21.1.el7.x86_64 (rhevh3-375.usersys.redhat.com) 13/08/18 _x86_64_ (2 CPU) 16:06:18 UID TGID TID %usr %system %guest %CPU CPU Command 16:06:18 107 19753 - 100.00 0.00 100.00 0.01 0 qemu-kvm 16:06:18 107 - 19753 0.00 0.00 0.00 0.00 0 |__qemu-kvm 16:06:18 107 - 19757 0.00 0.00 0.00 0.00 0 |__qemu-kvm 16:06:18 107 - 19758 0.00 0.00 0.00 0.00 0 |__IO 16:06:18 107 - 19762 0.00 0.00 0.00 0.00 0 |__CPU 16:06:18 107 - 19765 0.00 0.00 0.00 0.00 0 |__SPICE 16:06:18 107 - 21882 0.00 0.00 0.00 0.00 0 |__worker