linux-kernel - Re: [RFC][PATCH 00/26] sched/numa

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Date:	Mon, 19 Mar 2012 14:26:31 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Dan Smith <danms@...ibm.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH 00/26] sched/numa

On Mon, 2012-03-19 at 14:04 +0100, Andrea Arcangeli wrote:
> If you boot with memcg compiled in, that's taking an equivalent amount
> of memory per-page.
> 
> If you can bear the memory loss when memcg is compiled in even when
> not enabled, you sure can bear it on NUMA systems that have lots of
> memory, so it's perfectly ok to sacrifice a bit of it so that it
> performs like not-NUMA but you still have more memory than not-NUMA.
> 
I think the overhead of memcg is quite insane as well. And no I cannot
bear that and have it disabled in all my kernels.

NUMA systems having lots of memory is a false argument, that doesn't
mean we can just waste tons of it, people pay good money for that
memory, they want to use it.

I fact, I know that HPC people want things like swap-over-nfs so they
can push infrequently running system crap out into swap so they can get
these few extra megabytes of memory. And you're proposing they give up
~100M just like that?

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