affinity stressor sets affinity of stress-ng and stops all cpus from being exercised

[Colin Ian King]

SRU Request [Cosmic]

== Justification ==

When running stress-ng with the affinity stressor, the autodetection of sched_setaffinity currently sets affinity to CPU 0 meaning that the stressors run in the session are pinned to CPU 0.

== Fix ==

Upstream commit http://kernel.ubuntu.com/git/cking/stress-ng.git/commit/?id=2fea5d0437e918c4cadaa81ba1c3e07073286eff

== Testing ==

Run:

stress-ng --affinity 1 --cpu 4

use top and see that only CPU 0 is being maxed out, other CPUs are less loaded. With the fix at least 4 CPUs are running the cpu stressor

== Regression Potential ==

The fix restores the stress-ng behavior prior to commit 31c7658927, the change is just in the affinity stressor and impact on other stressors with changed functionality is zero. Users of stress-ng with this fix will see their machines being loaded in a more fair and balanced way and stress-ng will max out CPUs, as was originally intended. Regression potential is therefore machines will hit thermal maximums on their CPUs.

----

the stress-affinity stressor checks to see if sched_setaffinity works, however, in doing so sets the CPU affinity to CPU 0 for all stressors because this is performed at the start of stress-ng and other stressors inherit this affinity setting. Fix this by getting and then setting the same affinity.

[Colin Ian King (colin-king)]

Fix committed:

http://kernel.ubuntu.com/git/cking/stress-ng.git/commit/?id=2fea5d0437e918c4cadaa81ba1c3e07073286eff

[Timo Aaltonen (tjaalton)]

please add the distro package to bugs, so that uploads to the devel series close bugs automatically and the SRU reviewer wouldn't have to go check what is fixed there

[Timo Aaltonen (tjaalton)]

Hello Colin, or anyone else affected,

Accepted stress-ng into cosmic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/stress-ng/0.09.42-1ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-cosmic to verification-done-cosmic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-cosmic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Colin Ian King (colin-king)]

verified fixed with 0.09.42-1ubuntu1 on cosmic

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for stress-ng has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Launchpad Janitor (janitor)]

This bug was fixed in the package stress-ng - 0.09.42-1ubuntu1

---------------
stress-ng (0.09.42-1ubuntu1) cosmic; urgency=medium

  * stress-affinity: fix set affinity setting across all
    stressors (LP: #1803322)
    - fixes --seq 0 affinity setting stopping all CPUs from being used
  * stress-seccomp: add sanity check to see if SECCOMP_SET_MODE_FILTER
    works (LP: #1801856)
    - fixes false failure errors if filtering is not enabled
  * stress-dev: remove FIBMAP ioctl on device (LP: #1800609)
    - fixes error of incorrect ioctl on block device
  * stress-revio: ensure fiemap extent struct is zero'd (LP: #1798566)
    - fixes fiemap ioctl failures because of garbage in struct

 -- Colin King <email address hidden> Wed, 14 Nov 2018 17:28:22 +0000