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    SubjectRE: [PATCH 4/4] zone_reclaim_mode is always 0 by default
    >>-----Original Message-----
    >>From: KOSAKI Motohiro [mailto:kosaki.motohiro@jp.fujitsu.com]
    >>Sent: 2009年5月19日 12:31
    >>To: Zhang, Yanmin
    >>Cc: kosaki.motohiro@jp.fujitsu.com; Wu, Fengguang; LKML; linux-mm; Andrew
    >>Morton; Rik van Riel; Christoph Lameter
    >>Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default
    >>
    >>> >>-----Original Message-----
    >>> >>From: KOSAKI Motohiro [mailto:kosaki.motohiro@jp.fujitsu.com]
    >>> >>Sent: 2009ト・ヤツ19ネユ 10:54
    >>> >>To: Wu, Fengguang
    >>> >>Cc: kosaki.motohiro@jp.fujitsu.com; LKML; linux-mm; Andrew Morton; Rik van
    >>> >>Riel; Christoph Lameter; Zhang, Yanmin
    >>> >>Subject: Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default
    >>> >>
    >>> >>> On Wed, May 13, 2009 at 12:08:12PM +0900, KOSAKI Motohiro wrote:
    >>> >>> > Subject: [PATCH] zone_reclaim_mode is always 0 by default
    >>> >>> >
    >>> >>> > Current linux policy is, if the machine has large remote node distance,
    >>> >>> > zone_reclaim_mode is enabled by default because we've be able to assume
    >>> >>Fortunately (or Unfortunately), typical workload and machine size had
    >>> >>significant mutuality.
    >>> >>Thus, the current default setting calculation had worked well in past days.
    >>> [YM] Your analysis is clear and deep.
    >>
    >>Thanks!
    >>
    >>
    >>> >>Now, it was breaked. What should we do?
    >>> >>Yanmin, We know 99% linux people use intel cpu and you are one of
    >>> >>most hard repeated testing
    >>> [YM] It's very easy to reproduce them on my machines. :) Sometimes, because
    >>the
    >>> issues only exist on machines with lots of cpu while other community
    >>developers
    >>> have no such environments.
    >>>
    >>>
    >>> guy in lkml and you have much test.
    >>> >>May I ask your tested machine and benchmark?
    >>> [YM] Usually I started lots of benchmark testing against the latest kernel,
    >>but
    >>> as for this issue, it's reported by a customer firstly. The customer runs
    >>apache
    >>> on Nehalem machines to access lots of files. So the issue is an example of
    >>file
    >>> server.
    >>
    >>hmmm.
    >>I'm surprised this report. I didn't know this problem. oh..
    [YM] Did you run file server workload on such NUMA machine with
    zone_reclaim_mode=1? If all nodes have the same memory, the behavior is
    obvious.


    >>
    >>Actually, I don't think apache is only file server.
    >>apache is one of killer application in linux. it run on very widely
    >>organization.
    [YM] I know that. Apache could support document, ecommerce, and lots of other
    usage models. What I mean is one of customers hit it with their
    workload.


    >>you think large machine don't run apache? I don't think so.
    >>
    >>
    >>
    >>> BTW, I found many test cases of fio have big drop after I upgraded BIOS of
    >>one
    >>> Nehalem machine. By checking vmstat data, I found almost a half memory is
    >>always free. It's also related to zone_reclaim_mode because new BIOS changes
    >>the node
    >>> distance to a large value. I use numactl --interleave=all to walkaround the
    >>problem temporarily.
    >>>
    >>> I have no HPC environment.
    >>
    >>Yeah, that's ok. I and cristoph have. My worries is my unknown workload become
    >>regression.
    >>so, May I assume you run your benchmark both zonre reclaim 0 and 1 and you
    >>haven't seen regression by non-zone reclaim mode?
    [YM] what is non-zone reclaim mode? When zone_reclaim_mode=0?
    I didn't do that intentionally. Currently I just make sure FIO has a big drop
    when zone_reclaim_mode=1. I might test it with other benchmarks on 2 Nehalem machines.


    >>if so, it encourage very much to me.
    >>
    >>if zone reclaim mode disabling don't have regression, I'll pushing to
    >>remove default zone reclaim mode completely again.
    [YM] I run lots of benchmarks, but it doesn't mean I run all benchmarks, especially
    no HPC.


    >>
    >>
    >>> >>if zone_reclaim=0 tendency workload is much than zone_reclaim=1 tendency
    >>> >>workload,
    >>> >> we can drop our afraid and we would prioritize your opinion, of cource.
    >>> So it seems only file servers have the issue currently.



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