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Date: Mon, 24 Oct 2005 15:40:40 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Scalability problem with Pthread Read/Write Locks
Message-ID: <20051024134040.GD24278@calimero.vinschen.de>
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On Oct 23 05:45, Johan De Taeye wrote:
> 
> My multi-threaded application is creating a lot of
> pthread_rwlock objects to protect access to my objects.
> I am noticing that this doesn't scale up well. As the number
> of active objects being created/changed/deleted increases
> into the thousands, the runtime performance degrades very
> badly.
> 
> When investigating the problem I noticed from the source code
> in the files winsup/cygwin/thread.h and
> winsup/cygwin/thread.cc that a static double-linked list
> (called rwlocks) is used to keep track of all rwlocks present
> in the process. Removal of an element in the list is O(n) and
> explains the behavior of my application.
> 
> When compiling under Linux no such scalability problems are
> found. (I believe the pthreads implementation there doesn't
> need to  keep track of the active rwlocks)
> 
> Finally the question: Could/should the =list= data structure
> be replaced with a =set= to provide better scalability?

Maybe, but http://cygwin.com/acronyms/#SHTDI.  A patch which optimizes
cases like this are always thoughtfully considered.  If you're willing
to help, have a look on http://cygwin.com/contrib.html.  However, I'd
think we shouldn't change this for the upcoming 1.5.19 release which
already contains a lot more changes than we had in mind once.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat, Inc.

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