linux-kernel - Re: [PATCH 0/63] Basic scheduler support for automatic NUMA balancing V9

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Message-ID: <20131009110353.GA19370@gmail.com>
Date:	Wed, 9 Oct 2013 13:03:54 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/63] Basic scheduler support for automatic NUMA
 balancing V9


* Mel Gorman <mgorman@...e.de> wrote:

> This series has roughly the same goals as previous versions despite the
> size. It reduces overhead of automatic balancing through scan rate reduction
> and the avoidance of TLB flushes. It selects a preferred node and moves tasks
> towards their memory as well as moving memory toward their task. It handles
> shared pages and groups related tasks together. Some problems such as shared
> page interleaving and properly dealing with processes that are larger than
> a node are being deferred. This version should be ready for wider testing
> in -tip.

Thanks Mel - the series looks really nice. I've applied the patches to 
tip:sched/core and will push them out later today if they pass testing 
here.

> Note that with kernel 3.12-rc3 that numa balancing will fail to boot if 
> CONFIG_JUMP_LABEL is configured. This is a separate bug that is 
> currently being dealt with.

Okay, this is about:

  https://lkml.org/lkml/2013/9/30/308

Note that Peter and me saw no crashes so far, and we boot with 
CONFIG_JUMP_LABEL=y and CONFIG_NUMA_BALANCING=y. It seems like an 
unrelated bug in any case, perhaps related to specific details in your 
kernel image?

2)

I also noticed a small Kconfig annoyance:

config NUMA_BALANCING_DEFAULT_ENABLED
        bool "Automatically enable NUMA aware memory/task placement"
        default y
        depends on NUMA_BALANCING
        help
          If set, autonumic NUMA balancing will be enabled if running on a NUMA
          machine.

config NUMA_BALANCING
        bool "Memory placement aware NUMA scheduler"
        depends on ARCH_SUPPORTS_NUMA_BALANCING
        depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
        depends on SMP && NUMA && MIGRATION
        help
          This option adds support for automatic NUM

the NUMA_BALANCING_DEFAULT_ENABLED option should come after the 
NUMA_BALANCING entries - things like 'make oldconfig' produce weird output 
otherwise.

3)

Plus in addition to PeterZ's build fix I noticed this new build warning on 
i386 UP kernels:

 kernel/sched/fair.c:819:22: warning: 'task_h_load' declared 'static' but never defined [-Wunused-function]

Introduced here I think:

    sched/numa: Use a system-wide search to find swap/migration candidates

Thanks,

	Ingo
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