Re: [PATCH] nohz1: Documentation

From: Kevin Hilman
Date: Fri Mar 22 2013 - 15:01:23 EST


>> >
>> > In the meantime, one approach is to bind all these SCHED_OTHER tasks
>> > to designated housekeeping CPU(s) that don't run your main workload.
>> One cannot bind kevent threads and other per cpu threads to another
>> processor. So right now there is no way to avoid this issue.
> Yep, my approach works only for those threads that are free to migrate.
> Of course, in some cases, you can avoid per-CPU threads running by pinning
> interrupts, avoiding certain operations in your workload, and so on.

Speaking of threads that are not free to migrate, you might add a bit to
the doc explaining that these various kernel threads that cannot migrate
are also potential sources of jitter and also reasons why a CPU may exit
(or not enter) full nohz mode.

And thanks a ton for writing up this detailed doc. Speaking as someone
trying to get full nohz working on a new arch (ARM), getting my head
around all of this has been challenging, and your doc is a great help.

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