Re: [RFC PATCH 0/9] Introduce housekeeping subsystem

[Chris Metcalf]

On 8/11/2017 2:36 AM, Mike Galbraith wrote:
> On Thu, 2017-08-10 at 09:57 -0400, Chris Metcalf wrote:
> > On 8/10/2017 8:54 AM, Frederic Weisbecker wrote:
> > > But perhaps I should add a new NO_HZ_FULL_BUT_HOUSEKEEPING option.
> > > Otherwise we'll change the meaning of NO_HZ_FULL_ALL way too much, to the point
> > > that its default behaviour will be the exact opposite of the current one: by default
> > > every CPU is housekeeping, so NO_HZ_FULL_ALL would have no effect anymore if we
> > > don't set housekeeping boot option.
> > Maybe a CONFIG_HOUSEKEEPING_BOOT_ONLY as a way to restrict housekeeping
> > by default to just the boot cpu.  In conjunction with NOHZ_FULL_ALL you would
> > then get the expected semantics.
> A big box with only the boot cpu for housekeeping is likely screwed.

Fair point - this kind of configuration would be primarily useful for
dedicated systems that were running a high-traffic-rate networking
application on many cores, for example.  In this mode you don't end up
putting a lot of burden on the housekeeping core.  In any case,
probably not worth adding an additional kernel config for.

--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com