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

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Message-ID: <alpine.DEB.2.20.1708111033440.2446@nuc-kabylake>
Date:   Fri, 11 Aug 2017 10:35:19 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     Chris Metcalf <cmetcalf@...lanox.com>
cc:     Mike Galbraith <efault@....de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, Rik van Riel <riel@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>
Subject: Re: [RFC PATCH 0/9] Introduce housekeeping subsystem

On Fri, 11 Aug 2017, Chris Metcalf wrote:

> > > 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.

The standard server config at this point is a two NUMA node with lots of
cores on each. For such a thing a single housekeeping cpu is usually
sufficient. Having a rather large number of NUMA nodes is unusual.

The question is also what is considered a "large" system at this point?
Lots of cores? Lots of NUMA nodes?

Ah, Chris since you are here: What is happening with the dataplane
patches?