From: ian AT cygnus DOT com (Ian Lance Taylor)
Subject: Re: Question about Sergey's heap change
7 Apr 1998 21:03:43 -0700
Message-ID: <199804080353.XAA23108.cygnus.cygwin32.developers@subrogation.cygnus.com>
References: <199804080141 DOT SAA28592 AT skaro DOT cygnus DOT com>
To: noer AT cygnus DOT com
Cc: cygwin32-developers AT cygnus DOT com, noer AT cygnus DOT com

   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.

Ian