EGL: add deferred saving of the cache

This change causes any insertions into the EGL cache to trigger an
attempt to save the cache contents to disk.  The save operation is
deferred to allow multiple cache insertions to be batched up.

Change-Id: I6cfec9c0dbbef94d3f8880860e2a365dccc296c7

Author: Jamie Gennis

opengl/libs/EGL/egl_cache.cpp

@@ -34,6 +34,9 @@ static const size_t maxTotalSize = 64 * 1024;
 static const char* cacheFileMagic = "EGL$";
 static const size_t cacheFileHeaderSize = 8;
 
+// The time in seconds to wait before saving newly inserted cache entries.
+static const unsigned int deferredSaveDelay = 4;
+
 // ----------------------------------------------------------------------------
 namespace android {
 // ----------------------------------------------------------------------------
@@ -128,6 +131,30 @@ void egl_cache_t::setBlob(const void* key, EGLsizei keySize, const void* value,
     if (mInitialized) {
         sp<BlobCache> bc = getBlobCacheLocked();
         bc->set(key, keySize, value, valueSize);
+
+        if (!mSavePending) {
+            class DeferredSaveThread : public Thread {
+            public:
+                DeferredSaveThread() : Thread(false) {}
+
+                virtual bool threadLoop() {
+                    sleep(deferredSaveDelay);
+                    egl_cache_t* c = egl_cache_t::get();
+                    Mutex::Autolock lock(c->mMutex);
+                    if (c->mInitialized) {
+                        c->saveBlobCacheLocked();
+                    }
+                    c->mSavePending = false;
+                    return false;
+                }
+            };
+
+            // The thread will hold a strong ref to itself until it has finished
+            // running, so there's no need to keep a ref around.
+            sp<Thread> deferredSaveThread(new DeferredSaveThread());
+            mSavePending = true;
+            deferredSaveThread->run();
+        }
     }
 }
 

opengl/libs/EGL/egl_cache.h

@@ -108,6 +108,13 @@ class EGLAPI egl_cache_t {
     // from disk.
     String8 mFilename;
 
+    // mSavePending indicates whether or not a deferred save operation is
+    // pending.  Each time a key/value pair is inserted into the cache via
+    // setBlob, a deferred save is initiated if one is not already pending.
+    // This will wait some amount of time and then trigger a save of the cache
+    // contents to disk.
+    bool mSavePending;
+
     // mMutex is the mutex used to prevent concurrent access to the member
     // variables. It must be locked whenever the member variables are accessed.
     mutable Mutex mMutex;