To: cygwin AT cygwin DOT com
Subject: Re: Excessive thrashing when popen()ing after a large malloc()
In-Reply-To: <4559D376.9030707@byu.net>
Message-Id: <20061114154207.3B49E148F021@u53026a.matapp.unimib.it>
Date: Tue, 14 Nov 2006 16:42:07 +0100 (CET)
From: grenie AT matapp DOT unimib DOT it (Loic Grenie)
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Precedence: bulk
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com

On Tue Nov 14 15:53:36 2006, Eric Blake (ebb9 AT byu DOT net ) wrote:
> According to Loic Grenie on 11/14/2006 4:12 AM:
>>    The subjects says it all: when a process has a large memory space,
>>   a popen() triggers a long disk thrashing. The result can clearly be
>>   seen iwth the allegated cygtharsh program (running with 1GB of memory,
>>   change the size of the malloc to roughly half your memory size):

> Indeed - the fork/exec model of the current popen implementation is harsh
> on large memory spaces, compared to your proposed spawn model.  While the
> idea may have merit, you have some work to do before a patch can be accepted.

    I did actually not submit a patch, I suggested a modification with some
  basic, untested, lines of code as a start.

>>   to something similar to (warning: untested, needs a char *cmd; at the
>>   beggining):

> Hint - popen is implemented in newlib, not cygwin, so you are posting to
> the wrong list.  Unless you provide a 'diff -u' patch, it is very
> difficult to see your changes in context.

    Sorry, I'll try to write there, with an additional diff -u.

> And admitting that your changes are untested is not a good sign for
> getting it approved.

    I'm not really "admitting", I am just expliciting that the patch is
  untested. I do not have the resources to build the thing.

      Sorry to have disturbed, happy cygwining,

         Loīc

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/