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Subject: Re: Cygwin multithreading performance
References: <CABPLASTtRK4mNxh0M_AnZgjJQ15kWPx+L=U=VCU3Wwi7jV_57A@mail.gmail.com> <564E3017.90205@maxrnd.com> <CABPLASTLrH_udLuu2F-m5P6dkENW1Z4YHEudp4NG0-FGLJgPMg@mail.gmail.com> <5650379B.4030405@maxrnd.com> <20151121105301.GE2755@calimero.vinschen.de>
To: cygwin@cygwin.com
From: Mark Geisert <mark@maxrnd.com>
Message-ID: <5652C402.7040006@maxrnd.com>
Date: Sun, 22 Nov 2015 23:45:06 -0800
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Corinna Vinschen wrote:
> On Nov 21 01:21, Mark Geisert wrote:
[...] so I wonder if there's
>> some unintentional serialization going on somewhere, but I don't know yet
>> how I could verify that theory.
>
> If I'm allowed to make an educated guess, the big serializer in Cygwin
> are probably the calls to malloc, calloc, realloc, free.  We desperately
> need a new malloc implementation better suited to multi-threading.

That's very helpful to know.  I'd want to first make sure the heavy lock 
activity I'm seeing in the traces really is due to malloc() and friends 
but I couldn't help a speculative search online for multithread-safe 
malloc().  These turned up:
     tcmalloc - part of google-perftools, requires libunwind, evidently 
not yet ported to Windows AFAICT,
     nedmalloc - http://www.nedprod.com/programs/portable/nedmalloc/
     ptmalloc - http://www.malloc.de/

The latter two are based on Doug Lea's dlmalloc which is also the basis 
of Cygwin's malloc() functions.  As I understand it, ptmalloc in one 
form or another has been part of glibc on Linux for some time.

So there may be a solution in sight if we need to go that direction.  Of 
course, SHTDI as usual :).

..mark

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