A simple load optimisation tool for Portal 2 on Linux.
This utility is obsolete. Its functionality is now part of SourceAutoRecord.
The library built, pathmatch_cache.so, should simply be injected into
the game process using LD_PRELOAD. This can be done by following these
steps:
- Place
pathmatch_cache.sointosteamapps/common/Portal 2/ - Edit the file
steamapps/common/Portal 2/portal2.sh - Beneath the line that reads
cd "$GAMEROOT", add the following line:export LD_PRELOAD="pathmatch_cache.so:$LD_PRELOAD" - Save this file, and start the game.
On my system, this managed to decrease my average load time in a normal singleplayer session from 3.9s to 1.6s (as reported by SAR).
Note that due to the implementation of this cache, it adds some small
limitations to what can be done in the game. Specifically, using a file
which you have just created - for instance, trying to run playdemo for
a demo you just recorded - may not be possible without restarting the
game.
When running on Linux, the Source Engine uses a small system called
pathmatch to simulate a case-insensitive filesystem, as Linux
filesystems are normally case-sensitive. This is effectively a long
recursive function, called for most stdio file/directory function
invocations. Due to how this function is implemented, it is incredibly
slow, performing thousands of calls to readdir. This is a major
contributor to the fact that map loads (and general engine performance)
are significantly slower on Linux than on Windows.
The solution to this slowdown is caching the pathmatch results. The
function can be found within the filesystem_stdio.so module of the
engine; by loading this module and scanning for the function's byte
sequence, we can overwrite its code with a simple trampoline which first
calls into a caching system.