[Vm-dev] Fwd: Only ever grows? (was: Re: [squeak-dev] how/where is memory returned to the OS?)

Igor Stasenko siguctua at gmail.com
Mon Oct 22 03:52:38 UTC 2012

This topic belongs to this list.

---------- Forwarded message ----------
From: Igor Stasenko <siguctua at gmail.com>
Date: 22 October 2012 05:36
Subject: Re: Only ever grows? (was: Re: [squeak-dev] how/where is
memory returned to the OS?)
To: ma.chris.m at gmail.com, The general-purpose Squeak developers list
<squeak-dev at lists.squeakfoundation.org>

On 22 October 2012 04:35, Chris Muller <asqueaker at gmail.com> wrote:
>> Unfortunately there is no easy fix , which will fit all possible use scenarios.
>> As you can see from comments in code, this feature was disabled on purpose
>> for cases when your application works extensively with external
>> resources/libraries,
>> which using malloc() a lot.
> You mean FFI?  Someone took the trouble to write this for the manpage.
>  My gut thinks FFI has been around longer than the releasing of memory
> feature -- not sure.
>        -mmap size[mk]
>               requests that a variable heap of at most  size  bytes  be  allo‐
>               cated.   (The  suffixes  are  as  described  for  the  '-memory'
>               option.)  squeak will initially allocate a heap  that  is  large
>               enough  to  hold the image, with a small amount of headroom.  If
>               at any time Squeak requires more memory for its image then addi‐
>               tional space will be allocated dynamically.  Likewise, when mem‐
>               ory is no longer needed it will deallocated and returned to  the
>               system.   The size argument places an upper limit on how big the
>               heap can grow in this fashion.  squeak uses a  dynamic  heap  by
>               default  with  the maximum size set to 75% of the available vir‐
>               tual memory or 1 gigabyte, whichever is smaller.
> Eliot, is the useMmap variable you referred to set by this argument?
> I tried launching my image with -mmap 700M but it still didn't seem to
> want to deallocate.
> Same with the Classic VM.

It is controlled by overallocateMemory flag,
which is not exposed via command-line options.

Here the patched file.
I added a new option -releaseUnusedMemory to turn this flag on.

I didn't tried to build VM with it, so don't blame me if it doesn't works :)

diff --git a/platforms/unix/vm/sqUnixMain.c b/platforms/unix/vm/sqUnixMain.c
index a593b2a..875bf0d 100644
--- a/platforms/unix/vm/sqUnixMain.c
+++ b/platforms/unix/vm/sqUnixMain.c
@@ -98,6 +98,7 @@ static char **squeakArgVec=   0;

 static int    extraMemory=     0;
        int    useMmap=         DefaultMmapSize * 1024 * 1024;
+extern int     overallocateMemory; /* defined in vm/sqUnixMemory.c */

 static int    useItimer=       1;      /* 0 to disable itimer-based clock */
 static int    installHandlers= 1;      /* 0 to disable sigusr1 &
sigsegv handlers */
@@ -1263,6 +1264,7 @@ static int vm_parseArgument(int argc, char **argv)
   /* vm arguments */

   if      (!strcmp(argv[0], "-help"))          { usage();
 return 1; }
+  else if (!strcmp(argv[0], "-releaseUnusedMemory") {
overallocateMemory = 1; return 1; }
   else if (!strcmp(argv[0], "-noevents"))      { noEvents      = 1;
 return 1; }
   else if (!strcmp(argv[0], "-nomixer"))       { noSoundMixer  = 1;
 return 1; }
   else if (!strcmp(argv[0], "-notimer"))       { useItimer     = 0;
 return 1; }

Best regards,
Igor Stasenko.

Best regards,
Igor Stasenko.
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