X-Recipient: archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status: No, hits=-0.9 required=5.0 	tests=AWL,BAYES_50,J_CHICKENPOX_42,SPF_PASS
X-Spam-Check-By: sourceware.org
From: Haojun Bao <baohaojun AT gmail DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Emacs can't start-process more than 30~40 processes
References: <83iqhlbgoc DOT fsf AT gmail DOT com> <4A6727A8 DOT 2090905 AT cornell DOT edu> 	<83iqhkur2h DOT fsf AT gmail DOT com> <834osy98jo DOT fsf_-_ AT gmail DOT com> 	<83tz0xtt6c DOT fsf AT gmail DOT com> <20090729023256 DOT GC11458 AT ednor DOT casa DOT cgf DOT cx>
Date: Wed, 29 Jul 2009 15:32:28 +0800
In-Reply-To: <20090729023256.GC11458@ednor.casa.cgf.cx> (Christopher Faylor's 	message of "Tue, 28 Jul 2009 22:32:56 -0400")
Message-ID: <838wi8vt9v.fsf@gmail.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.96 (cygwin)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-IsSubscribed: yes
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Precedence: bulk
List-Id: <cygwin.cygwin.com>
List-Unsubscribe: <mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com> writes:

> On Tue, Jul 28, 2009 at 10:52:44AM +0800, Haojun Bao wrote:
>>I have debugged it again, and I think I have more clue. I have read the
>>how-cygheap-works.txt, and this might be a known problem.
>>
>>It's because the cygheap space has been used up. With Procexp, I can see
>>cygwin1.dll is based 0x61000000, with size 0x300000 (3M). When segfault
>>is about to happen, cygheap_max is 0x6164e924, and the _csbrk is called
>>with a increase of 
>>    (gdb) p sbs
>>    $16 = 65544
>>This will increase cyghead to 0x6165e92c, but from Proxexp I can see
>>cygncurses-9.dll is based at 0x61650000.
>>
>>Besides, this code snippet from pipe.cc fhandler_pipe::create didn't
>>check for NULL pointer, and directly caused the segfault.
>>
>>      fhs[0] = (fhandler_pipe *) build_fh_dev (*piper_dev);
>>      fhs[1] = (fhandler_pipe *) build_fh_dev (*pipew_dev);
>>
>>//bhj: we should check NULL here.
>
> Not necessarily.  We don't expect these functions to return NULL.  It
> would be interesting to know how many fds are open at this point.  If it
> is a large number then maybe we have to start enforcing an fd max.  If
> it is a "small" number then something is wrong and we're allocating too
> much of the cygheap.  The cygheap was always supposed to be relatively
> small.  Maybe we're abusing it too much in 1.7.

There are quite some fds. In start-process, emacs will allocate 1 PTY
and 1 pipe for each process it starts.

Each fhandler_base is about 32K, but the _csbrk must allocate 65544
bytes for it.

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