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Refine document about IRQBALANCE_BANNED_CPUS #90

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merged 1 commit into from Feb 28, 2019

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ryncsn commented Feb 26, 2019

There is no declaration about how irqbalance deal with isolated CPUs or
adaptive-ticks CPUs, and how IRQBALANCE_BANNED_CPUS will override the
behavior of auto-banning of such CPUs. Refine the document to avoid
confusion.

Signed-off-by: Kairui Song kasong@redhat.com

Refine document about IRQBALANCE_BANNED_CPUS
There is no declaration about how irqbalance deal with isolated CPUs or
adaptive-ticks CPUs, and how IRQBALANCE_BANNED_CPUS will override the
behavior of auto-banning of such CPUs. Refine the document to avoid
confusion.

Signed-off-by: Kairui Song <kasong@redhat.com>
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nhorman commented Feb 26, 2019

I appreciate the patch, but the text isn't quite accurate. the banned cpu mask is or-ed with the isolated and adaptive tick cpu sets. It would be more accurate to leave out the text about the banned cpu set being unspecified and say instead that isolated and adaptive tick cpus are always considered to be banned.

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ryncsn commented Feb 28, 2019

Thanks for the review, but I did get what you mean by:

the banned cpu mask is or-ed with the isolated and adaptive tick cpu sets

The doc text is based on the commit message of ca5a3f1 and 2dddcfe, they says that use of IRQBALANCE_BANNED_CPUS enviroment variable will disable the auto detect of cpu masks, and that's how the function setup_banned_cpus() works.

For example I isolated cpu 0-3:
Auto-detect worked well:

[root@localhost ~]# irqbalance --debug
Isolated CPUs: 0000000f
Adaptive-ticks CPUs: 00000000
Banned CPUs: 0000000f

IRQBALANCE_BANNED_CPUS did disable the auto-detection:

[root@localhost ~]# export IRQBALANCE_BANNED_CPUS="0000010"
[root@localhost ~]# irqbalance --debug
Isolated CPUs: 00000000
Adaptive-ticks CPUs: 00000000
Banned CPUs: 00000010

I could post another patch to fix the behavior instead.

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nhorman commented Feb 28, 2019

Oh yo're right, I missed the goto out in that commit. This is ok

@nhorman nhorman merged commit b24dfeb into Irqbalance:master Feb 28, 2019

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