id,summary,reporter,owner,description,type,status,priority,milestone,component,resolution,keywords,cc,phab_field
2020,[PATCH] Memory Pool + Bucket Allocator,Jorma Rebane,Jorma Rebane,"This patch adds a custom high performance memory pool implementation to 0 A.D. In addition an STL-compatible custom allocator (bucket_allocator<T>) is included.

Adding memory pools will greatly improve the overall performance of 0 A.D. In order to make this convenient a wrapper header ""ps_stl.h"" is also included that wraps the STL containers with the custom bucket allocator.


The bucket allocator uses Thread-Local-Storage to create a collection of memory-pools. It is called a bucket allocator because all allocations are divided into sized 'buckets':
{{{
Buckets [0..24]		4 8 12 16 20 24 
Buckets [25..64]	32 40 48 56 64 
Buckets [65..128]	80 96 112 128 
Buckets [129..256]	160 192 224 256 
Buckets [257..1024]	384 512 640 768 896 1024
}}}

Names of the wrapped stl containers in ps_stl.h:
{{{
ps::vector<T>
ps::list<T>
ps::basic_string<T>
ps::string
ps::wstring
ps::map<Key, T>
ps::set<T>
ps::unordered_map<Key, T>
ps::unordered_set<T>
}}}


These are the performance comparisons from the patch test suite:
{{{
    >> RELEASE Debugger Attached
    std_alloc fragmented:     2614ms
    std_alloc growshrink:     8156ms
    std_alloc temporaries:    86ms
    tls_bucket fragmented:    7ms
    tls_bucket growshrink:    4ms
    tls_bucket temporaries:   3ms
    stress_test std::stl:     628ms
    stress_test ps::stl:      48ms
     
    >> RELEASE No debugger
    std_alloc fragmented:     15ms
    std_alloc growshrink:     13ms
    std_alloc temporaries:    9ms
    tls_bucket fragmented:    5ms
    tls_bucket growshrink:    4ms
    tls_bucket temporaries:   4ms
    stress_test std::stl:     76ms
    stress_test ps::stl:      41ms
}}}

After adding this patch, the 0 A.D. source can be changed iteratively to include the new ps_stl.h wrapped containers without having to change the whole codebase.",enhancement,new,Must Have,Alpha 14,Core engine,,patch review performance memory,,