Re: [PATCH 4/4] nohz: New option to force all CPUs in full dynticksrange

[Christoph Lameter]

On Tue, 9 Apr 2013, Paul Gortmaker wrote:

> > 2. Avoid the setting of cpus entirely? If full nohz mode is desired
> > then pick one cpu (f.e. the first one or the one that is used for xtime
> > updates) and then make all other cpus nohz. Set the affinity mask for the
> > rcuoXXX threads to that cpu.
>
> I can imagine people with multi socket systems wanting to have
> a system partitioned with one "normal" core per physical socket,
> for timekeeping, RCU threads, etc, but #2 would prevent that.

That is a good point. The kernel needs to run per node threads for I/O and
reclaim which could have their home there. Just had some bad experience
with latency introduced by the block layer redirecting I/O to the first
processor of a node. Maybe we can adopt that convention and relocate
kernel processing as much as possible to the first processor of a
node?


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