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git-svn-id: https://profuse.googlecode.com/svn/branches/v2@209 aa027e90-d47c-11dd-86d7-074df07e0730
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ksherlock
parent
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commit
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@ -6,46 +6,13 @@
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#include <sys/mman.h>
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#include <unistd.h>
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#include <Cache/BlockCache.h>
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#include <Device/BlockDevice.h>
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#include <Device/BlockCache.h>
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#include <ProFUSE/Exception.h>
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#include <ProFUSE/auto.h>
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/*
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* Note -- everything is assumed to be single-threaded.
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*
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*/
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/*
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* The primary purpose of the block cache is not as a cache
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* (the OS probably does a decent job of that) but rather to
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* simplify read/writes. Blocks will always be accessed by
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* pointer, so any updates will be shared.
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* For memory mapped prodos-order files, MappedBlockCache just
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* returns a pointer to the memory.
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* For dos-order, nibblized, or raw devices, ConcreteBlockCache
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* uses an approach similar to minix (although the buffer pool will
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* expand if needed).
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*
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* _buffers is a vector of all buffers and only exists to make
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* freeing them easier.
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* _hashTable is a simple hashtable of loaded blocks.
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* _first and _last are a double-linked list of unused blocks, stored
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* in lru order.
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*
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* The Entry struct contains the buffer, the block, a dirty flag, and an in-use
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* count as well as pointer for the hashtable and lru list.
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* When a block is loaded, it is stored in the _hashTable. It remains in the
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* hash table when the in-use count goes to 0 (it will also be added to the
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* end of the lru list).
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*
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* dirty buffers are only written to disk in 3 scenarios:
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* a) sync() is called
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* b) the cache is deleted
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* c) a buffer is re-used from the lru list.
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*/
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using namespace Device;
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@ -56,7 +23,7 @@ using ProFUSE::POSIXException;
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#pragma mark -
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#pragma mark BlockCache
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BlockCache::~BlockCache(BlockDevice *device)
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BlockCache::BlockCache(BlockDevice *device)
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{
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_device = _device;
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_blocks = device->blocks();
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@ -81,334 +48,3 @@ void BlockCache::read(unsigned block, void *bp)
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std::memcpy(bp, address, 512);
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release(block, false);
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}
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#pragma mark -
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#pragma mark MappedBlockCache
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MappedBlockCache::MappedBlockCache(void *data, unsigned blocks)
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{
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_blocks = blocks;
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_data = (uint8_t *)data;
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}
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void MappedBlockCache::write()
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{
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// TODO...
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}
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void *MappedBlockCache::load(unsigned block)
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{
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#undef __METHOD__
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#define __METHOD__ "MappedBlockCache::load"
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if (block >= _blocks)
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throw Exception(__METHOD__ ": Invalid block.");
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return _data + block * 512;
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}
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void MappedBlockCache::unload(unsigned block, bool dirty)
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{
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#undef __METHOD__
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#define __METHOD__ "MappedBlockCache::unload"
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if (!dirty) return;
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// msync must be page-size aligned.
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unsigned pagesize = ::getpagesize();
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unsigned offset = block * 512;
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void *address = _data + offset / pagesize * pagesize;
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unsigned length = offset % pagesize + 512;
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if (::msync(address, length, MS_ASYNC) < 0)
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{
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throw POSIXException(__METHOD__ ": msync failed.", errno);
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}
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}
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#pragma mark -
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#pragma mark ConcreteBlockCache
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typedef std::vector<BlockCache::Entry *>::iterator EntryIter;
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ConcreteBlockCache::ConcreteBlockCache(BlockDevice *device, unsigned size) :
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BlockCache(device)
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{
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if (size < 16) size = 16;
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std::memset(_hashTable, 0, sizeof(Entry *) * HashTableSize);
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for (unsigned i = 0; i < size; ++i)
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{
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Entry *e = new Entry;
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std::memset(e, 0, sizeof(Entry));
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_buffers.push_back(e);
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}
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_first = _last = NULL;
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_first = _buffers.front();
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_last = _buffers.back();
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// form a chain....
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for (unsigned i = 0; i < size; ++i)
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{
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Entry *e = _buffers[i];
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if (i > 0) e->prev = _buffers[i - 1];
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if (i < size - 1) e->next = _buffers[i + 1];
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}
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}
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ConcreteBlockCache::~ConcreteBlockCache()
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{
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EntryIter iter;
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for (iter = _buffers.begin(); iter != _buffers.end(); ++iter)
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{
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Entry *e = *iter;
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if (e->dirty)
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{
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_device->write(e->block, e->buffer);
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}
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delete e;
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}
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_device->sync();
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}
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ConcreteBlockCache::sync()
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{
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EntryIter iter;
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for (iter = _buffers.begin(); iter != _buffers.end(); ++iter)
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{
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Entry *e = *iter;
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if (e->dirty)
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{
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_device->write(e->block, e->buffer);
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e->dirty = false;
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}
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}
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_device->sync();
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}
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void ConcreteBlockCache::write(unsigned block, const void *bp)
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{
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FileEntry *e = findEntry();
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if (e)
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{
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e->dirty = true;
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std::memcpy(e->buffer, bp, 512);
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return;
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}
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// returns a new entry not in the hashtable or the linked list.
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// we add it to both.
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e = newEntry(block);
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e->count = 0;
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e->dirty = true;
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std::memcpy(e->buffer, bp, 512);
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addEntry(e);
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setLast(e);
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}
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void ConcreteBlockCache::markDirty(unsigned block)
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{
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Entry *e = findEntry(block);
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if (e) e->dirty = true;
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// error otherwise?
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}
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void ConcreteBlockCache::release(unsigned block, bool dirty)
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{
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Entry *e = findEntry(block);
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if (e)
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{
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if (dirty) e->dirty = true;
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decrementCount(e);
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}
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// error otherwise?
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}
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void *ConcreteBlockCache::acquire(unsigned block)
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{
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Entry *e = findEntry(block);
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if (e)
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{
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incrementCount(e);
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return e->buffer;
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}
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// returns a new entry, not in hash table, not in free list.
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e = newEntry(block);
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_device->read(block, e->buffer);
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addEntry(e);
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return e->buffer;
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}
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unsigned ConcreteBlockCache::hashFunction(unsigned block)
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{
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return block % HashTableSize;
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}
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/*
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* remove a block from the hashtable
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* and write to dick if dirty.
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*/
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void removeEntry(unsigned block)
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{
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Entry *e;
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Entry *prev;
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unsigned hash = hashFunction(block);
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e = _hashTable[hash];
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if (!e) return;
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// head pointer, special case.
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if (e->block == block)
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{
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_hashTable[hash] = e->nextHash;
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e->nextHash = NULL;
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return;
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}
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for(;;)
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{
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prev = e;
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e = e->next;
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if (!e) break;
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if (e->block == block)
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{
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prev->nextHash = e->nextHash;
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e->nextHash = NULL;
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break;
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}
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}
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}
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void ConcreteBlockCache::addEntry(Entry *e)
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{
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unsigned hash = hashFunction(e->block);
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e->nextHash = _hashTable[hash];
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_hashTable[hash] = e;
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}
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// increment the count and remove from the free list
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// if necessary.
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void ConcreteBlockCache::incrementCount(Entry *e)
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{
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if (e->count == 0)
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{
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Entry *prev = e->prev;
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Entry *next = e->next;
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e->prev = e->next = NULL;
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if (prev) prev->next = next;
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if (next) next->prev = prev;
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if (_first == e) _first = next;
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if (_last == e) _last = prev;
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}
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e->count = e->count + 1;
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}
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// decrement the count. If it goes to 0,
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// add it as the last block entry.
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void ConcreteBlockCache::decrementCount(Entry *e)
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{
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e->count = e->count - 1;
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if (e->count == 0)
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{
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if (_last == NULL)
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{
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_first = _last = e;
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return;
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}
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e->prev = _last;
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_last = e;
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}
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}
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Entry *ConcreteBlockCache::newEntry(unsigned block)
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{
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Entry *e;
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if (_first)
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{
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e = _first;
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if (_first == _last)
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{
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_first = _last = NULL;
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}
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else
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{
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_first = e->next;
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_first->prev = NULL;
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}
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if (e->dirty)
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{
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_device->write(e->block, e->buffer);
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e->dirty = false;
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}
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removeEntry(e->block);
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}
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else
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{
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e = new Entry;
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_buffers.push_back(e);
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}
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e->next = NULL;
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e->prev= NULL;
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e->nextHash = NULL;
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e->count = 1;
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e->block = block;
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e->dirty = false;
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return e;
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}
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void ConcreteBlockCache::setLast(Entry *e)
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{
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if (_last == NULL)
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{
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_first = _last = e;
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return;
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}
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e->prev = _last;
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_last->next = e;
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_last = e;
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}
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@ -54,7 +54,7 @@ using ProFUSE::Exception;
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using ProFUSE::POSIXException;
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typedef std::vector<BlockCache::Entry *>::iterator EntryIter;
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typedef std::vector<ConcreteBlockCache::Entry *>::iterator EntryIter;
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@ -106,7 +106,7 @@ ConcreteBlockCache::~ConcreteBlockCache()
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}
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ConcreteBlockCache::sync()
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void ConcreteBlockCache::sync()
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{
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EntryIter iter;
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for (iter = _buffers.begin(); iter != _buffers.end(); ++iter)
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@ -125,7 +125,7 @@ ConcreteBlockCache::sync()
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void ConcreteBlockCache::write(unsigned block, const void *bp)
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{
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FileEntry *e = findEntry();
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Entry *e = findEntry(block);
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if (e)
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{
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@ -167,7 +167,7 @@ void ConcreteBlockCache::release(unsigned block, int flags)
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decrementCount(e);
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if (flags & kCommitNow)
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if (flags & kBlockCommitNow)
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{
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_device->write(block, e->buffer);
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e->dirty = false;
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@ -206,7 +206,7 @@ unsigned ConcreteBlockCache::hashFunction(unsigned block)
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* remove a block from the hashtable
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* and write to dick if dirty.
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*/
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void removeEntry(unsigned block)
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void ConcreteBlockCache::removeEntry(unsigned block)
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{
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Entry *e;
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Entry *prev;
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@ -283,7 +283,7 @@ void ConcreteBlockCache::decrementCount(Entry *e)
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}
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}
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Entry *ConcreteBlockCache::newEntry(unsigned block)
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ConcreteBlockCache::Entry *ConcreteBlockCache::newEntry(unsigned block)
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{
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Entry *e;
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@ -351,3 +351,4 @@ void ConcreteBlockCache::setFirst(Entry *e)
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_first->prev = e;
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_first = e;
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}
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@ -58,8 +58,10 @@ private:
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void setLast(Entry *);
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void setFirst(Entry *);
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incrementCount(Entry *);
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decrementCount(Entry *);
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void incrementCount(Entry *);
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void decrementCount(Entry *);
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};
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}
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#endif
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