linux-kernel - Re: vmstat: On demand vmstat workers V5

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Message-ID: <alpine.DEB.2.10.1405291121400.12545@gentwo.org>
Date:	Thu, 29 May 2014 11:24:15 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tejun Heo <tj@...nel.org>, John Stultz <johnstul@...ibm.com>,
	Mike Frysinger <vapier@...too.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, hughd@...gle.com,
	viresh.kumar@...aro.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org
Subject: Re: vmstat: On demand vmstat workers V5

On Thu, 29 May 2014, Frederic Weisbecker wrote:

> > Well yes and I am tying directly into that scheme there in cpu.c to
> > display the active vmstat threads in sysfs. so its the same.
>
> I don't think so. Or is there something in vmstat that cpumask_var_t
> definition depends upon?

This patch definitely ties the vmstat cpumask into the scheme in cpu.c

> > I would like to have some way to display the activities on cpus in /sysfs
> > like I have done here with the active vmstat workers.
> >
> > What I think we need is display cpumasks for
> >
> > 1. Cpus where the tick is currently off
> > 2. Cpus that have dynticks enabled.
> > 3. Cpus that are idle
>
> You should find all that in /proc/timer_list

True. I could actually drop the vmstat cpumask support.

> Now for CPUs that have full dynticks enabled, we probably need something
> in sysfs. We could dump the nohz cpumask somewhere. For now you can only grep
> the dmesg

There is a nohz mode in /proc/timer_list right?

> > 4. Cpus that are used for RCU.
>
> So, you mean those that aren't in extended grace period (between rcu_user_enter()/exit
> or rcu_idle_enter/exit)?

No I mean cpus that have their RCU processing directed to another
processor.

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