From: jeffdbREMOVETHIS AT goodnet DOT com (Mikey)
Subject: Re:  Sergeys temp fix for heap split
8 Apr 1998 08:47:25 -0700
Message-ID: <3530961a.128404303.cygnus.cygwin32.developers@smtp.goodnet.com>
References: <3 DOT 0 DOT 5 DOT 32 DOT 19980408103122 DOT 00a07e80 AT pop DOT ma DOT ultranet DOT com>
Reply-To: jeffdbREMOVETHIS AT goodnet DOT com
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To: cygwin32-developers AT cygnus DOT com

win95b
winsup-980401
seems to work fine, the memory is reserved, and the paging file
stays the same size.

On Wed, 08 Apr 1998 10:31:22 -0400, you wrote:

>At 09:01 AM 4/8/98 -0400, cgf AT cygnus DOT com wrote:
>>>From: ian AT cygnus DOT com (Ian Lance Taylor)
>>>Date: 7 Apr 1998 21:03:43 -0700
>>>
>>>>From: Geoffrey Noer <noer AT cygnus DOT com>
>>>>Date: Tue, 7 Apr 1998 18:41:15 -0700 (PDT)
>>>
>>>>Sergey Okhapkin wrote:
>>>>> 
>>>>> Now I know why _every_ cygwin process have a splitted heap if it allocates 
>>>>> more than heap_chunk_size bytes of memory (but I will not tell you why this 
>>>>> happens - think yourself!-) Here is the temporary fix - reserve a large 
>>>>> amount of memory for heap to avoid fork problem. The fix doesn't affect 
>>>>> performance.
>>>>> 
>>>>> H:\usr\src\cygnus\cdk\winsup>diff -u shared.cc.orig shared.cc
>>>>> --- shared.cc.orig      Wed Feb 11 06:15:08 1998
>>>>> +++ shared.cc   Tue Mar 24 10:44:55 1998
>>>>> @@ -96,7 +96,7 @@
>>>>> 
>>>>>    reg_session reg;
>>>>> 
>>>>> -  heap_chunk_in_mb = reg.get_key ().get_int ("heap_chunk_in_mb", 8);
>>>>> +  heap_chunk_in_mb = reg.get_key ().get_int ("heap_chunk_in_mb", 128);
>>>>>    if (heap_chunk_in_mb < 4)
>>>>>      {
>>>>>        heap_chunk_in_mb = 4;
>>>>
>>>>Are there reasons why I shouldn't make this change?
>>>
>>>On a traditional Unix system, making this change would mean that every
>>>process would require 128 MB in the swap file, and your system would
>>>rapidly run out of swap space.  I don't know how the Windows
>>>equivalent of a swap file works, so I don't know whether there would
>>>be any equivalent problem.
>>
>>Since the this just essentially sets aside a contiguous address range I
>>could envision an OS which would be intelligent enough to avoid allocating
>>swap space until parts of the memory region were committed.  I'm having
>>a difficult time, however, imagining a *Windows* operating system that
>>would be this intelligent.
>
>I believe the NT VMM allows you to do this.  But you're right, I'd be
>surprised to find out that Win95 can handle this properly.  Then again,
>I haven't checked it myself yet!:-)
>
>
>Larry Hall                              lhall AT rfk DOT com
>RFK Partners, Inc.                      (781) 239-1053
>8 Grove Street                          (781) 239-1655 - FAX
>Wellesley, MA  02181                    http://www.rfk.com


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(jeffdbREMOVETHIS AT netzone DOT com)
delete REMOVETHIS from the above to reply
         Mikey