5 ms·

I was under the impression that most large projects end up having to write a custom memory allocator, but after a few random probes into the source I didn't see

by afhof 15y ago

I was under the impression that most large projects end up having to write a custom memory allocator, but after a few random probes into the source I didn't see anything that stood out. Did I just miss it, or did they use the built in one?

ars 15y ago
Why do you have that impression? That makes very little sense to do - every single project? Don't you think someone would have released a library to implement the "new and improved allocator" if everyone needs to use it?
- vilya 15y ago
  That has been borne out by my experience so far too. There have been several successful efforts at writing better performing general-purpose allocators: * TCMalloc (http://goog-perftools.sourceforge.net/doc/tcmalloc.html) * jemalloc (http://www.canonware.com/jemalloc/) There's a great Facebook Engineering blog post about jemalloc which describes why a fast allocator is needed & why the standard malloc is not always sufficient: https://www.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919 https://www.facebook.com/notes/facebook-engineering/scalable...
  - forrestthewoods 15y ago
    I've worked with several projects where a TCMalloc based allocator (threaded) was used to great success. A simple switch to DLMalloc (non-threaded) can also provide a significant performance boost. Moderate usage of STL can do nasty, nasty things to memory performance. In one case a game I worked on ran at 5-10fps and a simple, fast change to DLMalloc instantly took perf to 60fps.
    - caf 15y ago
      It's worth noting that at least on some platforms the system malloc is dlmalloc (presuming that DL is Doug Lea).
      - iso8859-1 15y ago
        Which platforms?
        caf 15y ago
        glibc's malloc has long been based on Doug Lea's malloc.
    - vetler 15y ago
      +1 for TCMalloc. We used TCMalloc at Opera Community[0], and they still might be using it there for all I know ... it greatly improved performance on our MySQL servers! [0]: http://my.opera.com/ http://my.opera.com/
      - Poyeyo 15y ago
        Aren't you using Percona build ?
        vetler 15y ago
        Not when I worked there, but it's a few years ago. Don't know what they use now.
- anaisbetts 15y ago
  Most game projects do end up having to write a custom allocator, due to very specific memory budgets, deterministic malloc/free perf requirements, and issues with fragmentation.
- danssig 15y ago
  No, the point of a custom allocator is writing one that works with your specific requirements. A general allocator will never be more efficient than a custom one designed for the specific task. It becomes just an issue of is the cost worth what the optimization buys you, and games are an area where you need every drop of speed you can get.
barrybe 15y ago
There's one here: https://github.com/TTimo/doom3.gpl/blob/master/neo/idlib/Heap.cpp https://github.com/TTimo/doom3.gpl/blob/master/neo/idlib/Hea... Surprisingly there's not a lot of platform-specific cruft in that code. The Xbox version of Doom3 must have been a separate code branch.
- deleted 15y ago
  [deleted]
- justinhj 15y ago
  the xbox version was done by another activision studio called vicarious visions. no xbox or playstation code can be released due to developer license agreements
deleted 15y ago
[deleted]
gurkendoktor 15y ago
Quake 2 didn't have its own memory allocator either. Maybe the system allocator(s) got better with the years. http://fabiensanglard.net/quake2/index.php http://fabiensanglard.net/quake2/index.php
- klodolph 15y ago
  I don't know which Quake 2 you are looking at. Do a code search for Z_TagMalloc and Hunk_Alloc.
  - gurkendoktor 15y ago
    To quote the review (which I've read more than the source): The Zone Memory Allocator(common.c: Z_Malloc, Z_Free, Z_TagMalloc , Z_FreeTags) is still here in Quake2 but it is pretty much useless: Tagging is never used and allocation/deallocation is build on top of malloc and free (I have no idea why id software decided to trust the C Standard Library at this point). The overflow detector (using the Z_MAGIC contant) is never used either. So, unless I totally misunderstand things, it is half C stdlib, half Hunk allocator?
mohaps 15y ago
idlib/Heap.h and idlib/Heap.cpp implement a replacement malloc/free. From the header comments: /* =============================================================================== Memory Management This is a replacement for the compiler heap code (i.e. "C" malloc() and free() calls). On average 2.5-3.0 times faster than MSVC malloc()/free(). Worst case performance is 1.65 times faster and best case > 70 times. =============================================================================== */

by afhof 15y ago

ars 15y ago

Why do you have that impression? That makes very little sense to do - every single project? Don't you think someone would have released a library to implement the "new and improved allocator" if everyone needs to use it?

vilya 15y ago
That has been borne out by my experience so far too. There have been several successful efforts at writing better performing general-purpose allocators: * TCMalloc (http://goog-perftools.sourceforge.net/doc/tcmalloc.html) * jemalloc (http://www.canonware.com/jemalloc/) There's a great Facebook Engineering blog post about jemalloc which describes why a fast allocator is needed & why the standard malloc is not always sufficient: https://www.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919 https://www.facebook.com/notes/facebook-engineering/scalable...
- forrestthewoods 15y ago
  I've worked with several projects where a TCMalloc based allocator (threaded) was used to great success. A simple switch to DLMalloc (non-threaded) can also provide a significant performance boost. Moderate usage of STL can do nasty, nasty things to memory performance. In one case a game I worked on ran at 5-10fps and a simple, fast change to DLMalloc instantly took perf to 60fps.
  - caf 15y ago
    It's worth noting that at least on some platforms the system malloc is dlmalloc (presuming that DL is Doug Lea).
    - iso8859-1 15y ago
      Which platforms?
      - caf 15y ago
        glibc's malloc has long been based on Doug Lea's malloc.
  - vetler 15y ago
    +1 for TCMalloc. We used TCMalloc at Opera Community[0], and they still might be using it there for all I know ... it greatly improved performance on our MySQL servers! [0]: http://my.opera.com/ http://my.opera.com/
    - Poyeyo 15y ago
      Aren't you using Percona build ?
      - vetler 15y ago
        Not when I worked there, but it's a few years ago. Don't know what they use now.
anaisbetts 15y ago
Most game projects do end up having to write a custom allocator, due to very specific memory budgets, deterministic malloc/free perf requirements, and issues with fragmentation.
danssig 15y ago
No, the point of a custom allocator is writing one that works with your specific requirements. A general allocator will never be more efficient than a custom one designed for the specific task. It becomes just an issue of is the cost worth what the optimization buys you, and games are an area where you need every drop of speed you can get.

barrybe 15y ago

There's one here: https://github.com/TTimo/doom3.gpl/blob/master/neo/idlib/Heap.cpp https://github.com/TTimo/doom3.gpl/blob/master/neo/idlib/Hea... Surprisingly there's not a lot of platform-specific cruft in that code. The Xbox version of Doom3 must have been a separate code branch.

deleted 15y ago
[deleted]
justinhj 15y ago
the xbox version was done by another activision studio called vicarious visions. no xbox or playstation code can be released due to developer license agreements

deleted 15y ago

[deleted]

gurkendoktor 15y ago

Quake 2 didn't have its own memory allocator either. Maybe the system allocator(s) got better with the years. http://fabiensanglard.net/quake2/index.php http://fabiensanglard.net/quake2/index.php

klodolph 15y ago
I don't know which Quake 2 you are looking at. Do a code search for Z_TagMalloc and Hunk_Alloc.
- gurkendoktor 15y ago
  To quote the review (which I've read more than the source): The Zone Memory Allocator(common.c: Z_Malloc, Z_Free, Z_TagMalloc , Z_FreeTags) is still here in Quake2 but it is pretty much useless: Tagging is never used and allocation/deallocation is build on top of malloc and free (I have no idea why id software decided to trust the C Standard Library at this point). The overflow detector (using the Z_MAGIC contant) is never used either. So, unless I totally misunderstand things, it is half C stdlib, half Hunk allocator?

mohaps 15y ago

idlib/Heap.h and idlib/Heap.cpp implement a replacement malloc/free. From the header comments: /* =============================================================================== Memory Management This is a replacement for the compiler heap code (i.e. "C" malloc() and free() calls). On average 2.5-3.0 times faster than MSVC malloc()/free(). Worst case performance is 1.65 times faster and best case > 70 times. =============================================================================== */