Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi

> >>> >>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.

I missed your point. I agree file server case is obvious. but I don't
think anybody oppose this.



> >>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.

hmhm, ok.


> >>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.

May I ask what is FIO?
File IO?


> >>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. 

Of cource. nobody can run all benchmark in the world :)



> >>> >>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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