CONCLUSION:
SHORT:
The performance related advantage of large page usage for randomly accessed data
in a big address range is significant, and i think it would be generally worth a
better implementation at operating system level.
DETAILED:
On current windows operating systems, the availability of unfragmented
continous large page blocks decreases over time.
There is a relation between, type and ammount of processes running on a system
and fragmentation progress.
This fragmentation, is generally irreversible and windows doesn't directly support
any defragmentation mechanism for physical RAM, currently.
To ensure a 100% availabilty of unfragmented physical RAM, the most effective approach would be
to allocate this RAM at system start, with the consequence, that this memory is no longer
available for other applications.
If enough memory is available, a good implementation could be a preallocation via creation
of a big large page section object and later mappings in process address space.
This little research project is closet for now, maybe i will continue it later,
if i find the time and new motivation.
Thanks for your attention, Fred41 :)
=======================================================================================================
... this is an experimental replacement for armas default custom memory allocator ...
This custom memory allocator is based on intel tbb malloc 4.2, updt. 2 and should work with arma server and client.
You can find the source code of intels tbb 4.2, updt. 2 here:
and some general infos about custom memory allocator for arma and the BIS interface description can be found here:
http://community.bistudio.com/wiki/ArmA_2:_Custom_Memory_Allocator
This project is covered by the same license as provided with the source code from intel (GPL 2.0).
Some small optimizations in the interface, a little workaround, adaption of some internal parameters and the fact,
that this allocator allocates memory regions in large pages (2048kB), instead of small pages (4kB) results in better performance,
compared with the default allocator tbb4malloc_bi.dll.
This allocator works best/only on 64 bit OS, with at least 8GB RAM.
HOW TO USE:
Copy tbbmalloc.dll in your arma3/dll directory.
append -malloc=tbbmalloc to your arma 3 start line.
tbbmalloc prefers to use RAM in large pages (2048kB instead of 4kB).
The use of large pages requires the lock pages in memory privilege for the arma user.
Make sure your arma user account has this privilege set in your local security policies settings (secpol.msc, restart required).
If your useraccount, which you use to start arma, is member of the administrator group, you have to start arma as administrator!
On client, i measured between 6-9% higher framerates with "Helos A3-bench". I noticed significant smoother gameplay (higher and more stable framerates). On server i have no benchmark, but it will accelerate here too, dependend on mission and server load.
This allocator logs some timing data to malloc_PIDX.log. The tbbmalloc logfile looks like in this example:
WindowsVersion: 6.1 ServicePack: 1.0 Typ: Desktop
process virt. address available: 3840
system physical RAM total: 16351
system physical RAM available: 12746
system committed limit: 40875
system committed peak: 6720
system committed current: 3612
system cache current: 2907
system handles: 9592
system processes: 43
system threads: 503
system uptime minutes: 50
SeLockMemoryPrivilege: granted, huge pages enabled
0.015s: 0.18ms 2048k at:0xffc00000 Alloc LP ( 2M)
0.015s: 0.00ms 128k at:0x00230000 Alloc SP ( 2M)
0.031s: 0.43ms 8192k at:0xff400000 Alloc LP ( 10M)
0.686s: 0.25ms 4096k at:0xff000000 Alloc LP ( 14M)
0.686s: 0.22ms 4096k at:0xfec00000 Alloc LP ( 18M)
0.686s: 0.21ms 4096k at:0xfe800000 Alloc LP ( 22M)
0.686s: 0.25ms 4096k at:0xfe400000 Alloc LP ( 26M)
0.967s: 0.32ms 4096k at:0xfe000000 Alloc LP ( 30M)
0.967s: 0.30ms 4096k at:0xfdc00000 Alloc LP ( 34M)
0.967s: 0.26ms 4096k at:0xfd800000 Alloc LP ( 38M)
.....
The line with SeLockMemoryPrivilege for example tells you, that the required privileg is set correctly.
(Alloc LP means large pages are allocated, SP means small pages)
IMPORTANT:
The goal of this little research project, is to verify the performance gain by using large pages for memory allocations and some other optimizations.
So this project will not provide a permanent replacement for the default memory allocator. Instead the results will be provided to BIS and hopefully help to improve the default memory allocator as part of the arma distribution.
Greets, Fred41