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Date: Tue, 26 Feb 2013 14:25:44 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: wrong performance of malloc/free under multi-threading
Message-ID: <20130226132544.GC2388@calimero.vinschen.de>
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References: <2265626 DOT 1033831361860540947 DOT herumi AT nifty DOT com> <20130226091403 DOT GB2388 AT calimero DOT vinschen DOT de> <512C9B00 DOT 5040506 AT breisch DOT org>
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On Feb 26 06:22, Chris J. Breisch wrote:
> On 2/26/2013 4:14 AM, Corinna Vinschen wrote:
> >On Feb 26 15:35, MITSUNARI Shigeo wrote:
> >>Hi.
> >>
> >>I found that the performance of malloc/free is wrong under multi-threading.
> >>The following test program reproduces the problem.
> >>
> >>The program repeats malloc and free under multi-thread.
> >>I measured the timing on Cygwin and Linux.
> >>
> >>timing(sec)|      threadNum
> >>-----------+----------+-------------
> >>            | 1        |     2
> >>-----------+----------+-------------
> >>Linux      | 1.45     |     0.69
> >>-----------+----------+-------------
> >>Cygwin     | 2.059    |    53.165
> >>-----------+----------+-------------
> >>
> >>The timing under Linux seems good scale but it is very wrong under Cygwin.
> >>Is it intentional behavior or do I use pthread in bad way?
> >
> >No, you're right.  This is easily reproducable.  I just had a look and
> >it seems that our malloc is really slow in multi-threading scenarios.
> >We're using Doug Lea's malloc unchanged with just additional locks
> >surrounding the underlying malloc/free calls.
> >
> >This appears to be a serious performance problem.  I just learned that
> >glibc uses another version of dlmalloc, called ptmalloc, which is a
> >derived version of dlmalloc optimized for multi-threading environments.
> >
> >Perhaps we have to do the same, but I don't know how long it takes to
> >port ptmalloc to Cygwin and obviously I don't know how big the
> >performance gain might be.
> >
> >
> >Corinna
> >
> 
> Does any host using newlib suffer from this problem, or is it
> exclusive to Cygwin?

This is Cygwin only.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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