initial commit, 4.5 stable

thirdparty/icu4c/common/unifiedcache.cpp

@@ -0,0 +1,521 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+******************************************************************************
+* Copyright (C) 2015, International Business Machines Corporation and
+* others. All Rights Reserved.
+******************************************************************************
+*
+* File unifiedcache.cpp
+******************************************************************************
+*/
+
+#include "unifiedcache.h"
+
+#include <algorithm>      // For std::max()
+#include <mutex>
+
+#include "uassert.h"
+#include "uhash.h"
+#include "ucln_cmn.h"
+
+static icu::UnifiedCache *gCache = nullptr;
+static std::mutex *gCacheMutex = nullptr;
+static std::condition_variable *gInProgressValueAddedCond;
+static icu::UInitOnce gCacheInitOnce {};
+
+static const int32_t MAX_EVICT_ITERATIONS = 10;
+static const int32_t DEFAULT_MAX_UNUSED = 1000;
+static const int32_t DEFAULT_PERCENTAGE_OF_IN_USE = 100;
+
+
+U_CDECL_BEGIN
+static UBool U_CALLCONV unifiedcache_cleanup() {
+    gCacheInitOnce.reset();
+    delete gCache;
+    gCache = nullptr;
+    gCacheMutex->~mutex();
+    gCacheMutex = nullptr;
+    gInProgressValueAddedCond->~condition_variable();
+    gInProgressValueAddedCond = nullptr;
+    return true;
+}
+U_CDECL_END
+
+
+U_NAMESPACE_BEGIN
+
+int32_t U_EXPORT2
+ucache_hashKeys(const UHashTok key) {
+    const CacheKeyBase* ckey = static_cast<const CacheKeyBase*>(key.pointer);
+    return ckey->hashCode();
+}
+
+UBool U_EXPORT2
+ucache_compareKeys(const UHashTok key1, const UHashTok key2) {
+    const CacheKeyBase* p1 = static_cast<const CacheKeyBase*>(key1.pointer);
+    const CacheKeyBase* p2 = static_cast<const CacheKeyBase*>(key2.pointer);
+    return *p1 == *p2;
+}
+
+void U_EXPORT2
+ucache_deleteKey(void *obj) {
+    CacheKeyBase* p = static_cast<CacheKeyBase*>(obj);
+    delete p;
+}
+
+CacheKeyBase::~CacheKeyBase() {
+}
+
+static void U_CALLCONV cacheInit(UErrorCode &status) {
+    U_ASSERT(gCache == nullptr);
+    ucln_common_registerCleanup(
+            UCLN_COMMON_UNIFIED_CACHE, unifiedcache_cleanup);
+
+    gCacheMutex = STATIC_NEW(std::mutex);
+    gInProgressValueAddedCond = STATIC_NEW(std::condition_variable);
+    gCache = new UnifiedCache(status);
+    if (gCache == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+    }
+    if (U_FAILURE(status)) {
+        delete gCache;
+        gCache = nullptr;
+        return;
+    }
+}
+
+UnifiedCache *UnifiedCache::getInstance(UErrorCode &status) {
+    umtx_initOnce(gCacheInitOnce, &cacheInit, status);
+    if (U_FAILURE(status)) {
+        return nullptr;
+    }
+    U_ASSERT(gCache != nullptr);
+    return gCache;
+}
+
+UnifiedCache::UnifiedCache(UErrorCode &status) :
+        fHashtable(nullptr),
+        fEvictPos(UHASH_FIRST),
+        fNumValuesTotal(0),
+        fNumValuesInUse(0),
+        fMaxUnused(DEFAULT_MAX_UNUSED),
+        fMaxPercentageOfInUse(DEFAULT_PERCENTAGE_OF_IN_USE),
+        fAutoEvictedCount(0),
+        fNoValue(nullptr) {
+    if (U_FAILURE(status)) {
+        return;
+    }
+    fNoValue = new SharedObject();
+    if (fNoValue == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    fNoValue->softRefCount = 1;  // Add fake references to prevent fNoValue from being deleted
+    fNoValue->hardRefCount = 1;  // when other references to it are removed.
+    fNoValue->cachePtr = this;
+
+    fHashtable = uhash_open(
+            &ucache_hashKeys,
+            &ucache_compareKeys,
+            nullptr,
+            &status);
+    if (U_FAILURE(status)) {
+        return;
+    }
+    uhash_setKeyDeleter(fHashtable, &ucache_deleteKey);
+}
+
+void UnifiedCache::setEvictionPolicy(
+        int32_t count, int32_t percentageOfInUseItems, UErrorCode &status) {
+    if (U_FAILURE(status)) {
+        return;
+    }
+    if (count < 0 || percentageOfInUseItems < 0) {
+        status = U_ILLEGAL_ARGUMENT_ERROR;
+        return;
+    }
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    fMaxUnused = count;
+    fMaxPercentageOfInUse = percentageOfInUseItems;
+}
+
+int32_t UnifiedCache::unusedCount() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    return uhash_count(fHashtable) - fNumValuesInUse;
+}
+
+int64_t UnifiedCache::autoEvictedCount() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    return fAutoEvictedCount;
+}
+
+int32_t UnifiedCache::keyCount() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    return uhash_count(fHashtable);
+}
+
+void UnifiedCache::flush() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+
+    // Use a loop in case cache items that are flushed held hard references to
+    // other cache items making those additional cache items eligible for
+    // flushing.
+    while (_flush(false));
+}
+
+void UnifiedCache::handleUnreferencedObject() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    --fNumValuesInUse;
+    _runEvictionSlice();
+}
+
+#ifdef UNIFIED_CACHE_DEBUG
+#include <stdio.h>
+
+void UnifiedCache::dump() {
+    UErrorCode status = U_ZERO_ERROR;
+    const UnifiedCache *cache = getInstance(status);
+    if (U_FAILURE(status)) {
+        fprintf(stderr, "Unified Cache: Error fetching cache.\n");
+        return;
+    }
+    cache->dumpContents();
+}
+
+void UnifiedCache::dumpContents() const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    _dumpContents();
+}
+
+// Dumps content of cache.
+// On entry, gCacheMutex must be held.
+// On exit, cache contents dumped to stderr.
+void UnifiedCache::_dumpContents() const {
+    int32_t pos = UHASH_FIRST;
+    const UHashElement *element = uhash_nextElement(fHashtable, &pos);
+    char buffer[256];
+    int32_t cnt = 0;
+    for (; element != nullptr; element = uhash_nextElement(fHashtable, &pos)) {
+        const SharedObject *sharedObject =
+                (const SharedObject *) element->value.pointer;
+        const CacheKeyBase *key =
+                (const CacheKeyBase *) element->key.pointer;
+        if (sharedObject->hasHardReferences()) {
+            ++cnt;
+            fprintf(
+                    stderr,
+                    "Unified Cache: Key '%s', error %d, value %p, total refcount %d, soft refcount %d\n",
+                    key->writeDescription(buffer, 256),
+                    key->creationStatus,
+                    sharedObject == fNoValue ? nullptr :sharedObject,
+                    sharedObject->getRefCount(),
+                    sharedObject->getSoftRefCount());
+        }
+    }
+    fprintf(stderr, "Unified Cache: %d out of a total of %d still have hard references\n", cnt, uhash_count(fHashtable));
+}
+#endif
+
+UnifiedCache::~UnifiedCache() {
+    // Try our best to clean up first.
+    flush();
+    {
+        // Now all that should be left in the cache are entries that refer to
+        // each other and entries with hard references from outside the cache.
+        // Nothing we can do about these so proceed to wipe out the cache.
+        std::lock_guard<std::mutex> lock(*gCacheMutex);
+        _flush(true);
+    }
+    uhash_close(fHashtable);
+    fHashtable = nullptr;
+    delete fNoValue;
+    fNoValue = nullptr;
+}
+
+const UHashElement *
+UnifiedCache::_nextElement() const {
+    const UHashElement *element = uhash_nextElement(fHashtable, &fEvictPos);
+    if (element == nullptr) {
+        fEvictPos = UHASH_FIRST;
+        return uhash_nextElement(fHashtable, &fEvictPos);
+    }
+    return element;
+}
+
+UBool UnifiedCache::_flush(UBool all) const {
+    UBool result = false;
+    int32_t origSize = uhash_count(fHashtable);
+    for (int32_t i = 0; i < origSize; ++i) {
+        const UHashElement *element = _nextElement();
+        if (element == nullptr) {
+            break;
+        }
+        if (all || _isEvictable(element)) {
+            const SharedObject *sharedObject =
+                    static_cast<const SharedObject*>(element->value.pointer);
+            U_ASSERT(sharedObject->cachePtr == this);
+            uhash_removeElement(fHashtable, element);
+            removeSoftRef(sharedObject);    // Deletes the sharedObject when softRefCount goes to zero.
+            result = true;
+        }
+    }
+    return result;
+}
+
+int32_t UnifiedCache::_computeCountOfItemsToEvict() const {
+    int32_t totalItems = uhash_count(fHashtable);
+    int32_t evictableItems = totalItems - fNumValuesInUse;
+
+    int32_t unusedLimitByPercentage = fNumValuesInUse * fMaxPercentageOfInUse / 100;
+    int32_t unusedLimit = std::max(unusedLimitByPercentage, fMaxUnused);
+    int32_t countOfItemsToEvict = std::max<int32_t>(0, evictableItems - unusedLimit);
+    return countOfItemsToEvict;
+}
+
+void UnifiedCache::_runEvictionSlice() const {
+    int32_t maxItemsToEvict = _computeCountOfItemsToEvict();
+    if (maxItemsToEvict <= 0) {
+        return;
+    }
+    for (int32_t i = 0; i < MAX_EVICT_ITERATIONS; ++i) {
+        const UHashElement *element = _nextElement();
+        if (element == nullptr) {
+            break;
+        }
+        if (_isEvictable(element)) {
+            const SharedObject *sharedObject =
+                    static_cast<const SharedObject*>(element->value.pointer);
+            uhash_removeElement(fHashtable, element);
+            removeSoftRef(sharedObject);   // Deletes sharedObject when SoftRefCount goes to zero.
+            ++fAutoEvictedCount;
+            if (--maxItemsToEvict == 0) {
+                break;
+            }
+        }
+    }
+}
+
+void UnifiedCache::_putNew(
+        const CacheKeyBase &key,
+        const SharedObject *value,
+        const UErrorCode creationStatus,
+        UErrorCode &status) const {
+    if (U_FAILURE(status)) {
+        return;
+    }
+    CacheKeyBase *keyToAdopt = key.clone();
+    if (keyToAdopt == nullptr) {
+        status = U_MEMORY_ALLOCATION_ERROR;
+        return;
+    }
+    keyToAdopt->fCreationStatus = creationStatus;
+    if (value->softRefCount == 0) {
+        _registerPrimary(keyToAdopt, value);
+    }
+    void *oldValue = uhash_put(fHashtable, keyToAdopt, (void *) value, &status);
+    U_ASSERT(oldValue == nullptr);
+    (void)oldValue;
+    if (U_SUCCESS(status)) {
+        value->softRefCount++;
+    }
+}
+
+void UnifiedCache::_putIfAbsentAndGet(
+        const CacheKeyBase &key,
+        const SharedObject *&value,
+        UErrorCode &status) const {
+    std::lock_guard<std::mutex> lock(*gCacheMutex);
+    const UHashElement *element = uhash_find(fHashtable, &key);
+    if (element != nullptr && !_inProgress(element)) {
+        _fetch(element, value, status);
+        return;
+    }
+    if (element == nullptr) {
+        UErrorCode putError = U_ZERO_ERROR;
+        // best-effort basis only.
+        _putNew(key, value, status, putError);
+    } else {
+        _put(element, value, status);
+    }
+    // Run an eviction slice. This will run even if we added a primary entry
+    // which doesn't increase the unused count, but that is still o.k
+    _runEvictionSlice();
+}
+
+
+UBool UnifiedCache::_poll(
+        const CacheKeyBase &key,
+        const SharedObject *&value,
+        UErrorCode &status) const {
+    U_ASSERT(value == nullptr);
+    U_ASSERT(status == U_ZERO_ERROR);
+    std::unique_lock<std::mutex> lock(*gCacheMutex);
+    const UHashElement *element = uhash_find(fHashtable, &key);
+
+    // If the hash table contains an inProgress placeholder entry for this key,
+    // this means that another thread is currently constructing the value object.
+    // Loop, waiting for that construction to complete.
+     while (element != nullptr && _inProgress(element)) {
+         gInProgressValueAddedCond->wait(lock);
+         element = uhash_find(fHashtable, &key);
+    }
+
+    // If the hash table contains an entry for the key,
+    // fetch out the contents and return them.
+    if (element != nullptr) {
+         _fetch(element, value, status);
+        return true;
+    }
+
+    // The hash table contained nothing for this key.
+    // Insert an inProgress place holder value.
+    // Our caller will create the final value and update the hash table.
+    _putNew(key, fNoValue, U_ZERO_ERROR, status);
+    return false;
+}
+
+void UnifiedCache::_get(
+        const CacheKeyBase &key,
+        const SharedObject *&value,
+        const void *creationContext,
+        UErrorCode &status) const {
+    U_ASSERT(value == nullptr);
+    U_ASSERT(status == U_ZERO_ERROR);
+    if (_poll(key, value, status)) {
+        if (value == fNoValue) {
+            SharedObject::clearPtr(value);
+        }
+        return;
+    }
+    if (U_FAILURE(status)) {
+        return;
+    }
+    value = key.createObject(creationContext, status);
+    U_ASSERT(value == nullptr || value->hasHardReferences());
+    U_ASSERT(value != nullptr || status != U_ZERO_ERROR);
+    if (value == nullptr) {
+        SharedObject::copyPtr(fNoValue, value);
+    }
+    _putIfAbsentAndGet(key, value, status);
+    if (value == fNoValue) {
+        SharedObject::clearPtr(value);
+    }
+}
+
+void UnifiedCache::_registerPrimary(
+            const CacheKeyBase *theKey, const SharedObject *value) const {
+    theKey->fIsPrimary = true;
+    value->cachePtr = this;
+    ++fNumValuesTotal;
+    ++fNumValuesInUse;
+}
+
+void UnifiedCache::_put(
+        const UHashElement *element,
+        const SharedObject *value,
+        const UErrorCode status) const {
+    U_ASSERT(_inProgress(element));
+    const CacheKeyBase* theKey = static_cast<const CacheKeyBase*>(element->key.pointer);
+    const SharedObject* oldValue = static_cast<const SharedObject*>(element->value.pointer);
+    theKey->fCreationStatus = status;
+    if (value->softRefCount == 0) {
+        _registerPrimary(theKey, value);
+    }
+    value->softRefCount++;
+    UHashElement *ptr = const_cast<UHashElement *>(element);
+    ptr->value.pointer = (void *) value;
+    U_ASSERT(oldValue == fNoValue);
+    removeSoftRef(oldValue);
+
+    // Tell waiting threads that we replace in-progress status with
+    // an error.
+    gInProgressValueAddedCond->notify_all();
+}
+
+void UnifiedCache::_fetch(
+        const UHashElement *element,
+        const SharedObject *&value,
+        UErrorCode &status) const {
+    const CacheKeyBase* theKey = static_cast<const CacheKeyBase*>(element->key.pointer);
+    status = theKey->fCreationStatus;
+
+    // Since we have the cache lock, calling regular SharedObject add/removeRef
+    // could cause us to deadlock on ourselves since they may need to lock
+    // the cache mutex.
+    removeHardRef(value);
+    value = static_cast<const SharedObject *>(element->value.pointer);
+    addHardRef(value);
+}
+
+
+UBool UnifiedCache::_inProgress(const UHashElement* element) const {
+    UErrorCode status = U_ZERO_ERROR;
+    const SharedObject * value = nullptr;
+    _fetch(element, value, status);
+    UBool result = _inProgress(value, status);
+    removeHardRef(value);
+    return result;
+}
+
+UBool UnifiedCache::_inProgress(
+        const SharedObject* theValue, UErrorCode creationStatus) const {
+    return (theValue == fNoValue && creationStatus == U_ZERO_ERROR);
+}
+
+UBool UnifiedCache::_isEvictable(const UHashElement *element) const
+{
+    const CacheKeyBase* theKey = static_cast<const CacheKeyBase*>(element->key.pointer);
+    const SharedObject* theValue = static_cast<const SharedObject*>(element->value.pointer);
+
+    // Entries that are under construction are never evictable
+    if (_inProgress(theValue, theKey->fCreationStatus)) {
+        return false;
+    }
+
+    // We can evict entries that are either not a primary or have just
+    // one reference (The one reference being from the cache itself).
+    return (!theKey->fIsPrimary || (theValue->softRefCount == 1 && theValue->noHardReferences()));
+}
+
+void UnifiedCache::removeSoftRef(const SharedObject *value) const {
+    U_ASSERT(value->cachePtr == this);
+    U_ASSERT(value->softRefCount > 0);
+    if (--value->softRefCount == 0) {
+        --fNumValuesTotal;
+        if (value->noHardReferences()) {
+            delete value;
+        } else {
+            // This path only happens from flush(all). Which only happens from the
+            // UnifiedCache destructor.  Nulling out value.cacheptr changes the behavior
+            // of value.removeRef(), causing the deletion to be done there.
+            value->cachePtr = nullptr;
+        }
+    }
+}
+
+int32_t UnifiedCache::removeHardRef(const SharedObject *value) const {
+    int refCount = 0;
+    if (value) {
+        refCount = umtx_atomic_dec(&value->hardRefCount);
+        U_ASSERT(refCount >= 0);
+        if (refCount == 0) {
+            --fNumValuesInUse;
+        }
+    }
+    return refCount;
+}
+
+int32_t UnifiedCache::addHardRef(const SharedObject *value) const {
+    int refCount = 0;
+    if (value) {
+        refCount = umtx_atomic_inc(&value->hardRefCount);
+        U_ASSERT(refCount >= 1);
+        if (refCount == 1) {
+            fNumValuesInUse++;
+        }
+    }
+    return refCount;
+}
+
+U_NAMESPACE_END