Entry cache:
* Moved hash computations out of the critical sections. * Replaced the LRU entry queue by an array of entry "generations", each containing a sparse array of entries of that generation. Whenever a generation is full, we clear the oldest generation and continue with that one. The main advantage of this algorithm is that entry cache's mutex could be replaced by an r/w lock, that most of the time only has to be read locked in Lookup(). This does dramatically decrease contention of that lock. The total -j8 Haiku image build speedup is marginal, but the kernel time drops about 7% (now being smaller than the real time). git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34950 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold
parent
74a2534a03
commit
1b1b94b85a
237
src/system/kernel/fs/EntryCache.cpp
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237
src/system/kernel/fs/EntryCache.cpp
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@ -0,0 +1,237 @@
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/*
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* Copyright 2008-2010, Ingo Weinhold, ingo_weinhold@gmx.de.
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* Distributed under the terms of the MIT License.
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*/
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#include "EntryCache.h"
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#include <new>
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static const int32 kEntriesPerGeneration = 1024;
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static const int32 kEntryNotInArray = -1;
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static const int32 kEntryRemoved = -2;
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// #pragma mark - EntryCacheGeneration
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EntryCacheGeneration::EntryCacheGeneration()
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:
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next_index(0),
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entries(NULL)
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{
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}
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EntryCacheGeneration::~EntryCacheGeneration()
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{
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delete[] entries;
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}
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status_t
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EntryCacheGeneration::Init()
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{
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entries = new(std::nothrow) EntryCacheEntry*[kEntriesPerGeneration];
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if (entries == NULL)
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return B_NO_MEMORY;
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memset(entries, 0, sizeof(EntryCacheEntry*) * kEntriesPerGeneration);
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return B_OK;
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}
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// #pragma mark - EntryCache
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EntryCache::EntryCache()
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:
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fCurrentGeneration(0)
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{
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rw_lock_init(&fLock, "entry cache");
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new(&fEntries) EntryTable;
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}
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EntryCache::~EntryCache()
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{
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// delete entries
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EntryCacheEntry* entry = fEntries.Clear(true);
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while (entry != NULL) {
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EntryCacheEntry* next = entry->hash_link;
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free(entry);
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entry = next;
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}
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rw_lock_destroy(&fLock);
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}
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status_t
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EntryCache::Init()
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{
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status_t error = fEntries.Init();
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if (error != B_OK)
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return error;
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for (int32 i = 0; i < kGenerationCount; i++) {
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error = fGenerations[i].Init();
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if (error != B_OK)
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return error;
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}
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return B_OK;
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}
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status_t
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EntryCache::Add(ino_t dirID, const char* name, ino_t nodeID)
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{
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EntryCacheKey key(dirID, name);
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WriteLocker _(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(key);
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if (entry != NULL) {
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entry->node_id = nodeID;
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if (entry->generation != fCurrentGeneration) {
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if (entry->index >= 0) {
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fGenerations[entry->generation].entries[entry->index] = NULL;
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_AddEntryToCurrentGeneration(entry);
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}
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}
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return B_OK;
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}
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entry = (EntryCacheEntry*)malloc(sizeof(EntryCacheEntry) + strlen(name));
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if (entry == NULL)
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return B_NO_MEMORY;
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entry->node_id = nodeID;
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entry->dir_id = dirID;
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entry->generation = fCurrentGeneration;
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entry->index = kEntryNotInArray;
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strcpy(entry->name, name);
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fEntries.Insert(entry);
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_AddEntryToCurrentGeneration(entry);
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return B_OK;
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}
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status_t
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EntryCache::Remove(ino_t dirID, const char* name)
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{
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EntryCacheKey key(dirID, name);
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WriteLocker writeLocker(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(key);
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if (entry == NULL)
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return B_ENTRY_NOT_FOUND;
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fEntries.Remove(entry);
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if (entry->index >= 0) {
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// remove the entry from its generation and delete it
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fGenerations[entry->generation].entries[entry->index] = NULL;
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free(entry);
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} else {
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// We can't free it, since another thread is about to try to move it
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// to another generation. We mark it removed and the other thread will
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// take care of deleting it.
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entry->index = kEntryRemoved;
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}
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return B_OK;
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}
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bool
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EntryCache::Lookup(ino_t dirID, const char* name, ino_t& _nodeID)
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{
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EntryCacheKey key(dirID, name);
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ReadLocker readLocker(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(key);
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if (entry == NULL)
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return false;
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int32 oldGeneration = atomic_set(&entry->generation, fCurrentGeneration);
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if (oldGeneration == fCurrentGeneration || entry->index < 0) {
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// The entry is already in the current generation or is being moved to
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// it by another thread.
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_nodeID = entry->node_id;
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return true;
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}
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// remove from old generation array
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fGenerations[oldGeneration].entries[entry->index] = NULL;
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entry->index = kEntryNotInArray;
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// add to the current generation
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int32 index = atomic_add(&fGenerations[oldGeneration].next_index, 1);
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if (index < kEntriesPerGeneration) {
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fGenerations[fCurrentGeneration].entries[index] = entry;
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entry->index = index;
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_nodeID = entry->node_id;
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return true;
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}
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// The current generation is full, so we probably need to clear the oldest
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// one to make room. We need the write lock for that.
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readLocker.Unlock();
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WriteLocker writeLocker(fLock);
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if (entry->index == kEntryRemoved) {
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// the entry has been removed in the meantime
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free(entry);
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return false;
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}
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_AddEntryToCurrentGeneration(entry);
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_nodeID = entry->node_id;
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return true;
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}
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void
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EntryCache::_AddEntryToCurrentGeneration(EntryCacheEntry* entry)
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{
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// the generation might not be full yet
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int32 index = fGenerations[fCurrentGeneration].next_index++;
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if (index < kEntriesPerGeneration) {
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fGenerations[fCurrentGeneration].entries[index] = entry;
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entry->generation = fCurrentGeneration;
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entry->index = index;
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return;
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}
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// we have to clear the oldest generation
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int32 newGeneration = (fCurrentGeneration + 1) % kGenerationCount;
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for (int32 i = 0; i < kEntriesPerGeneration; i++) {
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EntryCacheEntry* otherEntry = fGenerations[newGeneration].entries[i];
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if (otherEntry == NULL)
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continue;
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fGenerations[newGeneration].entries[i] = NULL;
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fEntries.Remove(otherEntry);
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free(otherEntry);
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}
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// set the new generation and add the entry
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fCurrentGeneration = newGeneration;
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fGenerations[newGeneration].next_index = 1;
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fGenerations[newGeneration].entries[0] = entry;
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entry->generation = newGeneration;
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entry->index = 0;
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}
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@ -1,5 +1,5 @@
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/*
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* Copyright 2008-2009, Ingo Weinhold, ingo_weinhold@gmx.de.
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* Copyright 2008-2010, Ingo Weinhold, ingo_weinhold@gmx.de.
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* Distributed under the terms of the MIT License.
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*/
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#ifndef ENTRY_CACHE_H
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@ -9,32 +9,45 @@
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#include <stdlib.h>
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#include <util/AutoLock.h>
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#include <util/DoublyLinkedList.h>
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#include <util/khash.h>
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#include <util/OpenHashTable.h>
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const static uint32 kMaxEntryCacheEntryCount = 8192;
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// Maximum number of entries per entry cache. It's a hard limit ATM.
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struct EntryCacheKey {
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EntryCacheKey(ino_t dirID, const char* name)
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:
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dir_id(dirID),
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name(name)
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{
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hash = (uint32)dir_id ^ (uint32)(dir_id >> 32) ^ hash_hash_string(name);
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// We cache the hash value, so we can easily compute it before
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// holding any locks.
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}
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ino_t dir_id;
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const char* name;
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size_t hash;
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};
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struct EntryCacheEntry : DoublyLinkedListLinkImpl<EntryCacheEntry> {
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EntryCacheEntry* hash_link;
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ino_t node_id;
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ino_t dir_id;
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char name[1];
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struct EntryCacheEntry {
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EntryCacheEntry* hash_link;
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ino_t node_id;
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ino_t dir_id;
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vint32 generation;
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vint32 index;
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char name[1];
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};
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struct EntryCacheGeneration {
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vint32 next_index;
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EntryCacheEntry** entries;
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EntryCacheGeneration();
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~EntryCacheGeneration();
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status_t Init();
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};
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@ -44,8 +57,7 @@ struct EntryCacheHashDefinition {
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uint32 HashKey(const EntryCacheKey& key) const
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{
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return (uint32)key.dir_id ^ (uint32)(key.dir_id >> 32)
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^ hash_hash_string(key.name);
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return key.hash;
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}
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size_t Hash(const EntryCacheEntry* value) const
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@ -69,102 +81,34 @@ struct EntryCacheHashDefinition {
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class EntryCache {
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public:
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EntryCache()
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{
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mutex_init(&fLock, "entry cache");
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EntryCache();
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~EntryCache();
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new(&fEntries) EntryTable;
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new(&fUsedEntries) EntryList;
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fEntryCount = 0;
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}
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status_t Init();
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~EntryCache()
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{
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while (EntryCacheEntry* entry = fUsedEntries.Head())
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_Remove(entry);
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status_t Add(ino_t dirID, const char* name,
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ino_t nodeID);
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mutex_destroy(&fLock);
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}
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status_t Remove(ino_t dirID, const char* name);
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status_t Init()
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{
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return fEntries.Init();
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}
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status_t Add(ino_t dirID, const char* name, ino_t nodeID)
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{
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MutexLocker _(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(EntryCacheKey(dirID, name));
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if (entry != NULL) {
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entry->node_id = nodeID;
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return B_OK;
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}
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if (fEntryCount >= kMaxEntryCacheEntryCount)
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_Remove(fUsedEntries.Head());
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entry = (EntryCacheEntry*)malloc(sizeof(EntryCacheEntry)
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+ strlen(name));
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if (entry == NULL)
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return B_NO_MEMORY;
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entry->node_id = nodeID;
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entry->dir_id = dirID;
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strcpy(entry->name, name);
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fEntries.Insert(entry);
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fUsedEntries.Add(entry);
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fEntryCount++;
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return B_OK;
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}
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status_t Remove(ino_t dirID, const char* name)
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{
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MutexLocker _(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(EntryCacheKey(dirID, name));
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if (entry == NULL)
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return B_ENTRY_NOT_FOUND;
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_Remove(entry);
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return B_OK;
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}
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bool Lookup(ino_t dirID, const char* name, ino_t& nodeID)
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{
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MutexLocker _(fLock);
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EntryCacheEntry* entry = fEntries.Lookup(EntryCacheKey(dirID, name));
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if (entry == NULL)
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return false;
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// requeue at the end
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fUsedEntries.Remove(entry);
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fUsedEntries.Add(entry);
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nodeID = entry->node_id;
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return true;
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}
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void _Remove(EntryCacheEntry* entry)
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{
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fEntries.Remove(entry);
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fUsedEntries.Remove(entry);
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free(entry);
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fEntryCount--;
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}
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bool Lookup(ino_t dirID, const char* name,
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ino_t& nodeID);
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private:
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typedef BOpenHashTable<EntryCacheHashDefinition> EntryTable;
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typedef DoublyLinkedList<EntryCacheEntry> EntryList;
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static const int32 kGenerationCount = 8;
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mutex fLock;
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EntryTable fEntries;
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EntryList fUsedEntries; // LRU queue (LRU entry at the head)
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uint32 fEntryCount;
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typedef BOpenHashTable<EntryCacheHashDefinition> EntryTable;
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typedef DoublyLinkedList<EntryCacheEntry> EntryList;
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private:
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void _AddEntryToCurrentGeneration(
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EntryCacheEntry* entry);
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private:
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rw_lock fLock;
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EntryTable fEntries;
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EntryCacheGeneration fGenerations[kGenerationCount];
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int32 fCurrentGeneration;
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};
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@ -8,6 +8,7 @@ UsePrivateHeaders net shared storage ;
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UseHeaders [ FDirName $(SUBDIR) $(DOTDOT) device_manager ] ;
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KernelMergeObject kernel_fs.o :
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EntryCache.cpp
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fd.cpp
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fifo.cpp
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KPath.cpp
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