linux-kernel - Re: [PATCH v16 00/13] support "task

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Date:   Mon, 6 Nov 2017 09:38:44 -0600 (CST)
From:   Christopher Lameter <cl@...ux.com>
To:     Chris Metcalf <cmetcalf@...lanox.com>
cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Francis Giraldeau <francis.giraldeau@...il.com>,
        linux-mm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v16 00/13] support "task_isolation" mode

On Fri, 3 Nov 2017, Chris Metcalf wrote:

> However, it doesn't seem possible to do the synchronous cancellation of
> the vmstat deferred work with irqs disabled, though if there's a way,
> it would be a little cleaner to do that; Christoph?  We can certainly
> update the statistics with interrupts disabled via
> refresh_cpu_vm_stats(false), but that's not sufficient.  For now, I

Callig quiet_vmstat() gives you the folding of the statistics without
the numa page allocator page cleanup. Leaving some pages in the queues
should not be that much of an issue.

> What about that d*mn 1 Hz clock?
>
> It's still there, so this code still requires some further work before
> it can actually get a process into long-term task isolation (without
> the obvious one-line kernel hack).  Frederic suggested a while ago
> forcing updates on cpustats was required as the last gating factor; do
> we think that is still true?  Christoph was working on this at one
> point - any progress from your point of view?

Well if you still have the 1 HZ clock then you can simply defer the numa
remote page cleanup of the page allocator to that the time you execute
that tick.