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Add a very naive block cache to the DiskBackedFileSystem.

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This would be a lot better as an LRU. Right now it's a 32-slot
hash table with random eviction.
This commit is contained in:
Andreas Kling 2018-10-25 12:35:49 +02:00
parent 82bbfa8496
commit fdc782c1d1
4 changed files with 36 additions and 3 deletions
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24
VirtualFileSystem/DiskBackedFileSystem.cpp
View file

@ -1,5 +1,11 @@
#include "DiskBackedFileSystem.h"
#ifdef SERENITY
#include "i386.h"
#else
typedef int InterruptDisabler;
#endif
//#define DBFS_DEBUG
DiskBackedFileSystem::DiskBackedFileSystem(RetainPtr<DiskDevice>&& device)
@ -36,11 +42,26 @@ ByteBuffer DiskBackedFileSystem::readBlock(unsigned index) const
#ifdef DBFS_DEBUG
kprintf("DiskBackedFileSystem::readBlock %u\n", index);
#endif
{
InterruptDisabler disabler;
auto it = m_blockCache.find(index);
if (it != m_blockCache.end()) {
return (*it).value;
}
}
auto buffer = ByteBuffer::createUninitialized(blockSize());
DiskOffset baseOffset = static_cast<DiskOffset>(index) * static_cast<DiskOffset>(blockSize());
auto* bufferPointer = buffer.pointer();
device().read(baseOffset, blockSize(), bufferPointer);
ASSERT(buffer.size() == blockSize());
{
InterruptDisabler disabler;
if (m_blockCache.size() >= 32)
m_blockCache.removeOneRandomly();
m_blockCache.set(index, buffer);
}
return buffer;
}
@ -74,5 +95,6 @@ void DiskBackedFileSystem::setBlockSize(unsigned blockSize)
void DiskBackedFileSystem::invalidateCaches()
{
// FIXME: Implement block cache.
InterruptDisabler disabler;
m_blockCache.clear();
}