linux-kernel - Re: [PATCH 0/4] munmap: Flexible mem unmap operation interface for scheduling latency

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Date:	Tue, 26 Apr 2011 10:20:58 +0900
From:	Geunsik Lim <leemgs1@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Darren Hart <dvhart@...ux.intel.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH 0/4] munmap: Flexible mem unmap operation interface for
 scheduling latency

On Tue, Apr 26, 2011 at 4:47 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> On Mon, 2011-04-25 at 19:44 +0900, Geunsik Lim wrote:
>>     Originally, We aim to not hold locks for too long (for scheduling latency reasons).
>>     So zap pages in ZAP_BLOCK_SIZE byte counts.
>>     This means we need to return the ending mmu_gather to the caller.
>
> Please have a look at the mmu_gather rewrite that hit -mm last week,
> that completely does away with ZAP_BLOCK_SIZE and renders these patches
> obsolete.
Yes. I also checked the patch that you stated at LKML mailing list previously.
In my thinking. I want to keep ZAP_BLOCK_SIZE related contents
that adjusted by Ingo, Robert, Andrew, and so on a long time ago
because I believe that we can overcome below problems sufficiently
in real world.
. LKML archive - http://lkml.org/lkml/2002/7/24/273
. LKML archive - http://lkml.org/lkml/2004/9/14/101

In my experience, I did overcome below problems with this patch
based on ZAP_BLOCK_SIZE.

1) To solve temporal CPU contention
    (e.g: case that cpu contention is 93% ~ 96% according to mmap/munmap
            to access mass files )
2) To get real-time or real-fast selectively on specified linux system
    ( demo: http://www.youtube.com/watch?v=PxcgvDTY5F0 )


>
> Also, -rt doesn't care since it already has preemptible mmu_gather.
>
> Furthermore:
>
>> +L:     linux-rt-users@...r.kernel.org
Sorry. I think that I have to add "linux-rt-users@...r.kernel.org" because  this
patch is related to scheduling latencies although this modification
is in ./linux-2.6/mm/ directory. I will remove "+L: linux-rt-users******" if
really linux-rt-users mailing list can not care.
>
> is complete crap, linux-rt-users is _NOT_ a development list.
>
>



-- 
Regards,
Geunsik Lim ( Samsung Electronics )
Blog : http://blog.naver.com/invain/
e-Mail: geunsik.lim@...sung.com
           leemgs@...il.com , leemgs1@...il.com
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