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Date:	Thu, 26 Nov 2015 10:34:27 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Cygwin multithreading performance
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On Nov 23 16:54, Mark Geisert wrote:
> John Hein wrote:
> >Mark Geisert wrote at 23:45 -0800 on Nov 22, 2015:
> >  > 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 Cy=
gwin
> >  > > are probably the calls to malloc, calloc, realloc, free.  We despe=
rately
> >  > > 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 frie=
nds
> >  > but I couldn't help a speculative search online for multithread-safe
> >  > malloc().  These turned up:
> >  >      tcmalloc - part of google-perftools, requires libunwind, eviden=
tly
> >  > 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 ba=
sis
> >  > 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
> >
> >Someone recently mentioned on this list they were working on porting
> >jemalloc.  That would be a good choice.
>=20
> Indeed; thanks for the reminder.  Somehow I hadn't followed that thread.

Indeed^2.  Did you look into the locking any further to see if there's
more than one culprit?  I guess we've a rather long way to a "lock-less
kernel"...


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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