Hello everybody.
There is no description in FPC doc's about this list subscription. May be it is better to put some doc's about this procedure in FPC doc's insteed of following sentense in readme.txt: Information about available lists and subscription can be found on http://lists.freepascal.org/mailman/listinfo
I do not have direct internet access. Can You send me answer by e-mail?

Regards,
Sergey Korshunoff

PS: I have modified version of heap manager for FPC (v1.00). In FPC 1.02 problem of memory fragmentation was solved in "FreeMem" procedure. I think this is not so good. In my version a merging is performed in "GetMem" procedure (when we looking freelists[0] for a free memory block).
This is faster (about 20% faster for a GetMem/FreeMem test cycle)

And my version do not allocate new memory from system if we have continius memory block of needed size (in v1.02 we do not merge blocks which start from some block in freelists[1..x])

Well. There is notes about my changes (related to v1.00): Sergey Korshunoff ():
1. Some constants moved from heaph.inc to this file.
2. Value returned by `SysMaxavail' is more correct now.
3. In SysGetMem:

       dec(internal_memavail,size);
     is moved near to succesful exit (or we need to decrement
     internal_memavail when we fail to allocate memory).
  4. Handle case when `HeapError' return value is not in [0,1,2].
  5. Now we repeat a full memory search path when `HeapError' say
     to try again. This is like Borland `GetMem' do it. And
     this allow us to handle a case when `HeapError' lead to
     a `FreeMem' call without adding any new memory from OS.
  6. BESTMATCH removed (it is time consuming procedure)
  7. SysGetMem now merges blocks.
  8. `heaporg', `heapptr' and `beforeheapendmask' are
     not used now and removed (new memory from system go directly
     to free list)
  9. Procedure ReAllocMem in TMemoryManager record now takes
     3rd paramater: a size of memory in old block which
     contain information (some time it is much faster do not
     to copy not used data from the old block)

10. Functions 'SysGetMem, Sys..' are removed from heaph.inc because you should use MemoryManager for this job.

syslinux.pp:
I replaced a call to syscall_nr_mmap by a call to syscall_nr_brk:
1) with syscall_nr_mmap first block of memory, reserved by FPC option "-Cs<n> set stack size to <n>",
and second memory block, asked from Linux, will never be merged.
2) Linux do not allow restrict amount of memory (used by program) if this memory is not allocated by syscall_nr_brk.

cmem.pp from source/packages:
CHeapSize and CMemAvail was added. CMEM do not return memory to system now (this behavior is like behavior of standard heap package). And now CMEM really do a work (there was some errors: before changes adding CMEM in Uses statements lead to not working program).

I don't know what the effect is of the above 8 points;
this should be looked at by Peter Vreman or Pierre Muller.

9. Procedure ReAllocMem in TMemoryManager record now takes 3rd paramater: a size of memory in old block which contain information (some time it is much faster do not to copy not used data from the old block)

AFAIK, this is not Delphi compatible; it should be removed again.

10. Functions 'SysGetMem, Sys..' are removed from heaph.inc because you should use MemoryManager for this job.

Not good, since someone may wish to install a memory manager that does not override all functions, so they may wish to have access to the old functions.

This is not good; the linux memory system used to use syscall_nr_brk, this was changed to syscall_nr_mmap() to be compatible with C libraries. C libraries use mmap(); if we use brk() then this creates conflicts.

Corrections to cmem may be sent to me; please send a context diff file.

Michael.

Can you send me a copy privately.

But these constants can be changed by the program. For example to allocate smaller memory blocks from the OS. And the returnnil const is necessary for tp compatibility in objects iirc.

These updates can be added easily.

> 5. Now we repeat a full memory search path when `HeapError' say > to try again. This is like Borland `GetMem' do it. And > this allow us to handle a case when `HeapError' lead to > a `FreeMem' call without adding any new memory from OS.

Must see code first

> 6. BESTMATCH removed (it is time consuming procedure)

It's a leftover from earilier implementation without merges.

> 7. SysGetMem now merges blocks.

This is good

> 8. `heaporg', `heapptr' and `beforeheapendmask' are > not used now and removed (new memory from system go directly > to free list)

Are you really sure the beforeheapendmask can be removed? Becuase the error it triggered was rather tricky:

When there are less bytes left then the size of tfreerecord (=12 bytes). Then you can't allocate a new block after it. And also not check if the block after it is used.

Example:

OS Block allocated of 1024 bytes.

You allocate 1016 bytes. Then you can't use the last 8 bytes and you need to set some flag that the block of 1016 bytes is the last block after which you can't checked.

Does it really speed up? Becuase it also adds some extra overhead to pass the size. And the extraneous moves are at max only 3 extra movsl assembler instructions.

Ever looked at heaptrc, then you know why they are exported.

brk() is slower. And more importantly it can't be used with dynamicly linked libraries.

Peter