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Changing the texture cache to be a proper LRU cache

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I change the currently used 'map' of textures to a queue (implemented as a
list), and then remove from the end of the queue when textures need removing
from the cache, and adding to the beginning of the queue.
The other operation that is needed is moving the texture to the
front of the list whenever it is used, so that frequently used
textures are not deleted.
In order to make that last operation effecient, I created
a map of the locations of these textures, and keep that
properly updated. This makes the accessing of a texture still O(1).
Then, in order to have the iterators remain valid through insertions
and deletions, I needed to implement the queue as a list.

The map and queue implementation is a standard way to implement
an LRU cache, just FYI. Not something I thought of all on my own.

Fixes issue #744
This commit is contained in:
matto 2015-10-04 17:41:25 -04:00 committed by Sergey Lipskiy
parent dee0cddf66
commit 4e415802fa
2 changed files with 35 additions and 20 deletions
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48
src/Textures.cpp
View File

@ -508,10 +508,11 @@ void TextureCache::destroy()
current[0] = current[1] = NULL;
for (Textures::const_iterator cur = m_textures.cbegin(); cur != m_textures.cend(); ++cur)
glDeleteTextures( 1, &cur->second.glName );
glDeleteTextures( 1, &cur->glName );
m_textures.clear();
m_lruTextureLocations.clear();
for (Textures::const_iterator cur = m_fbTextures.cbegin(); cur != m_fbTextures.cend(); ++cur)
for (FBTextures::const_iterator cur = m_fbTextures.cbegin(); cur != m_fbTextures.cend(); ++cur)
glDeleteTextures( 1, &cur->second.glName );
m_fbTextures.clear();
@ -522,11 +523,14 @@ void TextureCache::_checkCacheSize()
{
if (m_cachedBytes <= m_maxBytes)
return;
Textures::const_iterator iter = m_textures.cend();
do {
--iter;
m_cachedBytes -= iter->second.textureBytes;
glDeleteTextures( 1, &iter->second.glName );
const CachedTexture& tex = *iter;
m_cachedBytes -= tex.textureBytes;
glDeleteTextures(1, &tex.glName);
m_lruTextureLocations.erase(tex.crc);
} while (m_cachedBytes > m_maxBytes && iter != m_textures.cbegin());
m_textures.erase(iter, m_textures.cend());
}
@ -538,16 +542,17 @@ CachedTexture * TextureCache::_addTexture(u32 _crc32)
_checkCacheSize();
GLuint glName;
glGenTextures(1, &glName);
m_textures.emplace(_crc32, glName);
CachedTexture & texture = m_textures.at(_crc32);
texture.crc = _crc32;
return &texture;
m_textures.emplace_front(glName);
Textures::iterator new_iter = m_textures.begin();
new_iter->crc = _crc32;
m_lruTextureLocations.insert(std::pair<u32, Textures::iterator>(_crc32, new_iter));
return &(*new_iter);
}
void TextureCache::removeFrameBufferTexture(CachedTexture * _pTexture)
{
Textures::const_iterator iter = m_fbTextures.find(_pTexture->glName);
assert(iter != m_fbTextures.end());
FBTextures::const_iterator iter = m_fbTextures.find(_pTexture->glName);
assert(iter != m_fbTextures.cend());
m_cachedBytes -= iter->second.textureBytes;
glDeleteTextures( 1, &iter->second.glName );
m_fbTextures.erase(iter);
@ -1265,9 +1270,12 @@ void TextureCache::_updateBackground()
u32 params[4] = {gSP.bgImage.width, gSP.bgImage.height, gSP.bgImage.format, gSP.bgImage.size};
crc = CRC_Calculate(crc, params, sizeof(u32)*4);
Textures::iterator iter = m_textures.find(crc);
if (iter != m_textures.end()) {
CachedTexture & current = iter->second;
Texture_Locations::iterator locations_iter = m_lruTextureLocations.find(crc);
if (locations_iter != m_lruTextureLocations.end()) {
Textures::iterator iter = locations_iter->second;
CachedTexture & current = *iter;
m_textures.splice(m_textures.begin(), m_textures, iter);
assert(current.width == gSP.bgImage.width);
assert(current.height == gSP.bgImage.height);
assert(current.format == gSP.bgImage.format);
@ -1331,10 +1339,11 @@ void TextureCache::_clear()
current[0] = current[1] = NULL;
for (Textures::const_iterator cur = m_textures.cbegin(); cur != m_textures.cend(); ++cur) {
m_cachedBytes -= cur->second.textureBytes;
glDeleteTextures(1, &cur->second.glName);
m_cachedBytes -= cur->textureBytes;
glDeleteTextures(1, &cur->glName);
}
m_textures.clear();
m_lruTextureLocations.clear();
}
void TextureCache::update(u32 _t)
@ -1414,9 +1423,12 @@ void TextureCache::update(u32 _t)
return;
}
Textures::iterator iter = m_textures.find(crc);
if (iter != m_textures.end()) {
CachedTexture & current = iter->second;
Texture_Locations::iterator locations_iter = m_lruTextureLocations.find(crc);
if (locations_iter != m_lruTextureLocations.end()) {
Textures::iterator iter = locations_iter->second;
CachedTexture & current = *iter;
m_textures.splice(m_textures.begin(), m_textures, iter);
assert(current.width == sizes.width);
assert(current.height == sizes.height);
assert(current.clampWidth == sizes.clampWidth);

7
src/Textures.h
View File

@ -82,9 +82,12 @@ private:
void _initDummyTexture(CachedTexture * _pDummy);
void _getTextureDestData(CachedTexture& tmptex, u32* pDest, GLuint glInternalFormat, GetTexelFunc GetTexel, u16* pLine);
typedef std::map<u32, CachedTexture> Textures;
typedef std::list<CachedTexture> Textures;
typedef std::map<u32, Textures::iterator> Texture_Locations;
typedef std::map<u32, CachedTexture> FBTextures;
Textures m_textures;
Textures m_fbTextures;
Texture_Locations m_lruTextureLocations;
FBTextures m_fbTextures;
CachedTexture * m_pDummy;
CachedTexture * m_pMSDummy;
u32 m_hits, m_misses;