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Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable

From: KOSAKI Motohiro <kosaki dot motohiro at gmail dot com>
To: Carlos O'Donell <carlos at systemhalted dot org>
Cc: Siddhesh Poyarekar <siddhesh at redhat dot com>, KOSAKI Motohiro <kosaki dot motohiro at gmail dot com>,Rich Felker <dalias at aerifal dot cx>, libc-alpha at sourceware dot org
Date: Mon, 13 Aug 2012 02:32:36 -0400
Subject: Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
References: <20120720223800.GB26330@sunsite.ms.mff.cuni.cz> <20120720224417.E8BEF2C0CA@topped-with-meat.com> <20120721061814.GC26330@sunsite.ms.mff.cuni.cz> <20120721133217.GY544@brightrain.aerifal.cx> <20120725183634.E0C5F2C0B1@topped-with-meat.com> <CAHGf_=qCMy6K1MD4miN65GkMSumYTtH23xoFrfmCuh=WjybAVA@mail.gmail.com> <20120730230006.355f9b67@spoyarek> <5016D012.5000101@gmail.com> <20120730191758.GX544@brightrain.aerifal.cx> <CAHGf_=rRm4B4YCZKgos5hWN_QTYV76fAxcegO7D3x=4_A88Rvw@mail.gmail.com> <20120731132705.GZ544@brightrain.aerifal.cx> <CAHGf_=pN3KJGL_V1tQ2+o0=-RY4q2du7PJDnak9y7xyzYiH1tQ@mail.gmail.com> <20120810235226.408e3cec@spoyarek> <CADZpyiz05WnMqrREEtSs+oW_0Ld6hnfxbmFMk_hKYL-P_gFTag@mail.gmail.com> <20120811205228.42ab905f@spoyarek> <CADZpyizkMLBGK13-h-YH_CpVgbcx3n7gbxYAwxzsdbiEJOMNjg@mail.gmail.com>

>> Based on this, I propose making the heap shrinking unconditionally use
>> mmap(PROT_NONE, MAP_FIXED). I have been using the attached patch to do
>> this since about 24 hours now on my Fedora 16 x86_64 without any
>> problems. I have also verified that the patch does not cause any
>> regressions in the testsuite.
> 
> This looks like a very reasonable solution.
> 
> Machines don't have infinite memory and we all want to get more out of
> our systems, and this patch is a step towards that goal.

Hmmm..

If I understand correctly, this patch revert following commit. So, I suggest
to confirm the reason why Jakub introduced it. I'm afraid he intended to 
improve multi threaded performance instead of single. (Again, MADV_DONTNEED 
has good multi thread performance than PROT_NONE.)

commit c7fd336280f2d88be4a22303199323718c8c3a28
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon May 7 15:30:57 2007 +0000


Thanks.

Follow-Ups:
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: Siddhesh Poyarekar
- [PATCH v2] Allow shrinking of arena heaps using mmap based onovercommit settings when available
  - From: Siddhesh Poyarekar

References:
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: KOSAKI Motohiro
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: Siddhesh Poyarekar
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: Carlos O'Donell
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: Siddhesh Poyarekar
- Re: [PATCH][RFC] Allow explicit shrinking of arena heaps using anenvironment variable
  - From: Carlos O'Donell

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