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Diffstat (limited to 'startupcache/StartupCache.h')
| -rw-r--r-- | startupcache/StartupCache.h | 299 |
1 files changed, 299 insertions, 0 deletions
diff --git a/startupcache/StartupCache.h b/startupcache/StartupCache.h new file mode 100644 index 0000000000..5894a1c9c9 --- /dev/null +++ b/startupcache/StartupCache.h @@ -0,0 +1,299 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef StartupCache_h_ +#define StartupCache_h_ + +#include <utility> + +#include "nsClassHashtable.h" +#include "nsComponentManagerUtils.h" +#include "nsTArray.h" +#include "nsTHashSet.h" +#include "nsTStringHasher.h" // mozilla::DefaultHasher<nsCString> +#include "nsZipArchive.h" +#include "nsITimer.h" +#include "nsIMemoryReporter.h" +#include "nsIObserverService.h" +#include "nsIObserver.h" +#include "nsIObjectOutputStream.h" +#include "nsIFile.h" +#include "mozilla/Attributes.h" +#include "mozilla/AutoMemMap.h" +#include "mozilla/Compression.h" +#include "mozilla/MemoryReporting.h" +#include "mozilla/Monitor.h" +#include "mozilla/Mutex.h" +#include "mozilla/Result.h" +#include "mozilla/UniquePtr.h" +#include "mozilla/UniquePtrExtensions.h" + +/** + * The StartupCache is a persistent cache of simple key-value pairs, + * where the keys are null-terminated c-strings and the values are + * arbitrary data, passed as a (char*, size) tuple. + * + * Clients should use the GetSingleton() static method to access the cache. It + * will be available from the end of XPCOM init (NS_InitXPCOM3 in + * XPCOMInit.cpp), until XPCOM shutdown begins. The GetSingleton() method will + * return null if the cache is unavailable. The cache is only provided for + * libxul builds -- it will fail to link in non-libxul builds. The XPCOM + * interface is provided only to allow compiled-code tests; clients should avoid + * using it. + * + * The API provided is very simple: GetBuffer() returns a buffer that was + * previously stored in the cache (if any), and PutBuffer() inserts a buffer + * into the cache. GetBuffer returns a new buffer, and the caller must take + * ownership of it. PutBuffer will assert if the client attempts to insert a + * buffer with the same name as an existing entry. The cache makes a copy of the + * passed-in buffer, so client retains ownership. + * + * InvalidateCache() may be called if a client suspects data corruption + * or wishes to invalidate for any other reason. This will remove all existing + * cache data. Additionally, the static method IgnoreDiskCache() can be called + * if it is believed that the on-disk cache file is itself corrupt. This call + * implicitly calls InvalidateCache (if the singleton has been initialized) to + * ensure any data already read from disk is discarded. The cache will not load + * data from the disk file until a successful write occurs. + * + * Finally, getDebugObjectOutputStream() allows debug code to wrap an + * objectstream with a debug objectstream, to check for multiply-referenced + * objects. These will generally fail to deserialize correctly, unless they are + * stateless singletons or the client maintains their own object data map for + * deserialization. + * + * Writes before the final-ui-startup notification are placed in an intermediate + * cache in memory, then written out to disk at a later time, to get writes off + * the startup path. In any case, clients should not rely on being able to + * GetBuffer() data that is written to the cache, since it may not have been + * written to disk or another client may have invalidated the cache. In other + * words, it should be used as a cache only, and not a reliable persistent + * store. + * + * Some utility functions are provided in StartupCacheUtils. These functions + * wrap the buffers into object streams, which may be useful for serializing + * objects. Note the above caution about multiply-referenced objects, though -- + * the streams are just as 'dumb' as the underlying buffers about + * multiply-referenced objects. They just provide some convenience in writing + * out data. + */ + +namespace mozilla { + +namespace scache { + +struct StartupCacheEntry { + UniqueFreePtr<char[]> mData; + uint32_t mOffset; + uint32_t mCompressedSize; + uint32_t mUncompressedSize; + int32_t mHeaderOffsetInFile; + int32_t mRequestedOrder; + bool mRequested; + + MOZ_IMPLICIT StartupCacheEntry(uint32_t aOffset, uint32_t aCompressedSize, + uint32_t aUncompressedSize) + : mData(nullptr), + mOffset(aOffset), + mCompressedSize(aCompressedSize), + mUncompressedSize(aUncompressedSize), + mHeaderOffsetInFile(0), + mRequestedOrder(0), + mRequested(false) {} + + StartupCacheEntry(UniqueFreePtr<char[]> aData, size_t aLength, + int32_t aRequestedOrder) + : mData(std::move(aData)), + mOffset(0), + mCompressedSize(0), + mUncompressedSize(aLength), + mHeaderOffsetInFile(0), + mRequestedOrder(0), + mRequested(true) {} + + // std::pair is not trivially move assignable/constructible, so make our own. + struct KeyValuePair { + const nsCString* first; + StartupCacheEntry* second; + KeyValuePair(const nsCString* aKeyPtr, StartupCacheEntry* aValuePtr) + : first(aKeyPtr), second(aValuePtr) {} + }; + static_assert(std::is_trivially_move_assignable<KeyValuePair>::value); + static_assert(std::is_trivially_move_constructible<KeyValuePair>::value); + + struct Comparator { + using Value = KeyValuePair; + + bool Equals(const Value& a, const Value& b) const { + return a.second->mRequestedOrder == b.second->mRequestedOrder; + } + + bool LessThan(const Value& a, const Value& b) const { + return a.second->mRequestedOrder < b.second->mRequestedOrder; + } + }; +}; + +// We don't want to refcount StartupCache, and ObserverService wants to +// refcount its listeners, so we'll let it refcount this instead. +class StartupCacheListener final : public nsIObserver { + ~StartupCacheListener() = default; + NS_DECL_THREADSAFE_ISUPPORTS + NS_DECL_NSIOBSERVER +}; + +class StartupCache : public nsIMemoryReporter { + friend class StartupCacheListener; + + public: + NS_DECL_THREADSAFE_ISUPPORTS + NS_DECL_NSIMEMORYREPORTER + + // StartupCache methods. See above comments for a more detailed description. + + // true if the archive has an entry for the buffer or not. + bool HasEntry(const char* id); + + // Returns a buffer that was previously stored, caller does not take ownership + nsresult GetBuffer(const char* id, const char** outbuf, uint32_t* length); + + // Stores a buffer. Caller yields ownership. + nsresult PutBuffer(const char* id, UniqueFreePtr<char[]>&& inbuf, + uint32_t length); + + // Removes the cache file. + void InvalidateCache(bool memoryOnly = false); + + // If some event knowingly re-generates the startup cache (like live language + // switching) count these events in order to allow them. + void CountAllowedInvalidation(); + + // For use during shutdown - this will write the startupcache's data + // to disk if the timer hasn't already gone off. + void MaybeInitShutdownWrite(); + + // For use during shutdown - ensure we complete the shutdown write + // before shutdown, even in the FastShutdown case. + void EnsureShutdownWriteComplete(); + + // Signal that data should not be loaded from the cache file + static void IgnoreDiskCache(); + + static bool GetIgnoreDiskCache(); + + // In DEBUG builds, returns a stream that will attempt to check for + // and disallow multiple writes of the same object. + nsresult GetDebugObjectOutputStream(nsIObjectOutputStream* aStream, + nsIObjectOutputStream** outStream); + + static StartupCache* GetSingletonNoInit(); + static StartupCache* GetSingleton(); + static void DeleteSingleton(); + + // This measures all the heap memory used by the StartupCache, i.e. it + // excludes the mapping. + size_t HeapSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const + MOZ_REQUIRES(mTableLock); + + bool ShouldCompactCache() MOZ_REQUIRES(mTableLock); + nsresult ResetStartupWriteTimerCheckingReadCount(); + nsresult ResetStartupWriteTimerAndLock(); + nsresult ResetStartupWriteTimer() MOZ_REQUIRES(mTableLock); + bool StartupWriteComplete(); + + private: + StartupCache(); + virtual ~StartupCache(); + + friend class StartupCacheInfo; + + Result<Ok, nsresult> LoadArchive() MOZ_REQUIRES(mTableLock); + nsresult Init(); + + // Returns a file pointer for the cache file with the given name in the + // current profile. + Result<nsCOMPtr<nsIFile>, nsresult> GetCacheFile(const nsAString& suffix); + + // Opens the cache file for reading. + Result<Ok, nsresult> OpenCache(); + + // Writes the cache to disk + Result<Ok, nsresult> WriteToDisk() MOZ_REQUIRES(mTableLock); + + void WaitOnPrefetch(); + void StartPrefetchMemory() MOZ_REQUIRES(mTableLock); + + static nsresult InitSingleton(); + static void WriteTimeout(nsITimer* aTimer, void* aClosure); + void MaybeWriteOffMainThread(); + void ThreadedPrefetch(uint8_t* aStart, size_t aSize); + + Monitor mPrefetchComplete{"StartupCachePrefetch"}; + bool mPrefetchInProgress MOZ_GUARDED_BY(mPrefetchComplete){false}; + + // This is normally accessed on MainThread, but WriteToDisk() can + // access it on other threads + HashMap<nsCString, StartupCacheEntry> mTable MOZ_GUARDED_BY(mTableLock); + // This owns references to the contents of tables which have been invalidated. + // In theory it grows forever if the cache is continually filled and then + // invalidated, but this should not happen in practice. Deleting old tables + // could create dangling pointers. RefPtrs could be introduced, but it would + // be a large amount of error-prone work to change. + nsTArray<decltype(mTable)> mOldTables MOZ_GUARDED_BY(mTableLock); + size_t mAllowedInvalidationsCount; + nsCOMPtr<nsIFile> mFile; + loader::AutoMemMap mCacheData MOZ_GUARDED_BY(mTableLock); + Mutex mTableLock; + + nsCOMPtr<nsIObserverService> mObserverService; + RefPtr<StartupCacheListener> mListener; + nsCOMPtr<nsITimer> mTimer; + + bool mDirty MOZ_GUARDED_BY(mTableLock); + bool mWrittenOnce MOZ_GUARDED_BY(mTableLock); + bool mCurTableReferenced MOZ_GUARDED_BY(mTableLock); + + uint32_t mRequestedCount; + size_t mCacheEntriesBaseOffset; + + static StaticRefPtr<StartupCache> gStartupCache; + static bool gShutdownInitiated; + static bool gIgnoreDiskCache; + static bool gFoundDiskCacheOnInit; + + UniquePtr<Compression::LZ4FrameDecompressionContext> mDecompressionContext; +#ifdef DEBUG + nsTHashSet<nsCOMPtr<nsISupports>> mWriteObjectMap; +#endif +}; + +// This debug outputstream attempts to detect if clients are writing multiple +// references to the same object. We only support that if that object +// is a singleton. +#ifdef DEBUG +class StartupCacheDebugOutputStream final : public nsIObjectOutputStream { + ~StartupCacheDebugOutputStream() = default; + + NS_DECL_ISUPPORTS + NS_DECL_NSIOBJECTOUTPUTSTREAM + + StartupCacheDebugOutputStream(nsIObjectOutputStream* binaryStream, + nsTHashSet<nsCOMPtr<nsISupports>>* objectMap) + : mBinaryStream(binaryStream), mObjectMap(objectMap) {} + + NS_FORWARD_SAFE_NSIBINARYOUTPUTSTREAM(mBinaryStream) + NS_FORWARD_SAFE_NSIOUTPUTSTREAM(mBinaryStream) + + bool CheckReferences(nsISupports* aObject); + + nsCOMPtr<nsIObjectOutputStream> mBinaryStream; + nsTHashSet<nsCOMPtr<nsISupports>>* mObjectMap; +}; +#endif // DEBUG + +} // namespace scache +} // namespace mozilla + +#endif // StartupCache_h_ |