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Bug 1377574 - iothread values' logic not quite clear
Summary: iothread values' logic not quite clear
Keywords:
Status: NEW
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: libcgroup
Version: 7.4
Hardware: x86_64
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Nikola Forró
QA Contact: Chao Ye
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-09-20 06:39 UTC by yisun
Modified: 2019-01-01 03:11 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
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Last Closed:
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Description yisun 2016-09-20 06:39:22 UTC
Description of problem:
iothread values' logic not quite clear

Version-Release number of selected component (if applicable):
kernel-3.10.0-508.el7.x86_64
libcgroup-0.41-11.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. # pwd
/sys/fs/cgroup/cpu,cpuacct/machine.slice/machine-qemu\x2d1\x2dvirtlabtestcopy.scope

2. # ll | egrep "vcpu|iothread|emulator"
drwxr-xr-x. 2 root root 0 Sep 20 13:40 emulator
drwxr-xr-x. 2 root root 0 Sep 20 13:51 iothread1
drwxr-xr-x. 2 root root 0 Sep 20 13:40 vcpu0
drwxr-xr-x. 2 root root 0 Sep 20 13:40 vcpu1
drwxr-xr-x. 2 root root 0 Sep 20 13:40 vcpu2
drwxr-xr-x. 2 root root 0 Sep 20 13:40 vcpu3

3. current cpu related values as follow:
# cat cpu.shares 
1024
# cat cpu.cfs_quota_us 
2500
# cat cpu.cfs_period_us 
100000
# cat vcpu*/cpu.cfs_quota_us
1000
1000
1000
1000
# cat vcpu*/cpu.cfs_period_us
100000
100000
100000
100000
# cat emulator*/cpu.cfs_quota_us
-1
# cat emulator*/cpu.cfs_period_us
100000
# cat iothread1/cpu.cfs_quota_us 
1300
# cat iothread1/cpu.cfs_period_us 
100000

4. try to set iothread1/cpu.cfs_period_us to 51998, it's failed
# echo 51998 > iothread1/cpu.cfs_period_us 
-bash: echo: write error: Invalid argument

5. try to set iothread1/cpu.cfs_period_us to 51999, it's successful
# echo 51999 > iothread1/cpu.cfs_period_us 

# cat iothread1/cpu.cfs_period_us 
51999

Actual results:
as step 4, echo 51998 > iothread1/cpu.cfs_period_us

Expected results:
why set 51998 failed but set 51999 successful? the logic is not quite clear. 

Additional info:
This is from bug 1356937


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