commit ea5baf2b7a2a65de6c886ba3b207b55752b58637
author David Stevens <stevensd@google.com> Tue Oct 20 15:00:41 2020 +0900
committer Sungtak Lee <taklee@google.com> Wed Dec 09 23:05:42 2020 +0000
tree 7a754deb55126269fb95be37f9d9541a37641fb7
parent 6d30324cdd4edde44994458d036422cbcd7b0c86

BufferPool: limit number of idle buffers in caches

Some systems have limits on the total number of graphics buffers that
can be allocated, not just the total size. When dealing with
particularly small buffers, the caches could end up retaining 1000s of
buffers.  This change adds an additional eviction trigger based on the
number of idle cached buffers.

Bug: 170702290
Bug: 171553040
Test: android.video.cts.VideoEncoderDecoderTest on ARCVM
Change-Id: If3f4433ba1794ccb624b864a56619c8613a315f2
(cherry picked from commit 0f50e523ef1404f9afbaa7b919e2801e5d94012a)
Merged-In: If3f4433ba1794ccb624b864a56619c8613a315f2
(cherry picked from commit d620a390daf48f122942ce5d08a40ff409bd6aa0)

media/bufferpool/2.0/AccessorImpl.cpp

diff --git a/media/bufferpool/2.0/AccessorImpl.cpp b/media/bufferpool/2.0/AccessorImpl.cpp
index 6111fea..1d2562e 100644
--- a/media/bufferpool/2.0/AccessorImpl.cpp
+++ b/media/bufferpool/2.0/AccessorImpl.cpp
@@ -39,6 +39,8 @@
 
     static constexpr size_t kMinAllocBytesForEviction = 1024*1024*15;
     static constexpr size_t kMinBufferCountForEviction = 25;
+    static constexpr size_t kMaxUnusedBufferCount = 64;
+    static constexpr size_t kUnusedBufferCountTarget = kMaxUnusedBufferCount - 16;
 
     static constexpr nsecs_t kEvictGranularityNs = 1000000000; // 1 sec
     static constexpr nsecs_t kEvictDurationNs = 5000000000; // 5 secs
@@ -724,9 +726,11 @@
 }
 
 void Accessor::Impl::BufferPool::cleanUp(bool clearCache) {
-    if (clearCache || mTimestampUs > mLastCleanUpUs + kCleanUpDurationUs) {
+    if (clearCache || mTimestampUs > mLastCleanUpUs + kCleanUpDurationUs ||
+            mStats.buffersNotInUse() > kMaxUnusedBufferCount) {
         mLastCleanUpUs = mTimestampUs;
-        if (mTimestampUs > mLastLogUs + kLogDurationUs) {
+        if (mTimestampUs > mLastLogUs + kLogDurationUs ||
+                mStats.buffersNotInUse() > kMaxUnusedBufferCount) {
             mLastLogUs = mTimestampUs;
             ALOGD("bufferpool2 %p : %zu(%zu size) total buffers - "
                   "%zu(%zu size) used buffers - %zu/%zu (recycle/alloc) - "
@@ -737,8 +741,9 @@
                   mStats.mTotalFetches, mStats.mTotalTransfers);
         }
         for (auto freeIt = mFreeBuffers.begin(); freeIt != mFreeBuffers.end();) {
-            if (!clearCache && (mStats.mSizeCached < kMinAllocBytesForEviction
-                    || mBuffers.size() < kMinBufferCountForEviction)) {
+            if (!clearCache && mStats.buffersNotInUse() <= kUnusedBufferCountTarget &&
+                    (mStats.mSizeCached < kMinAllocBytesForEviction ||
+                     mBuffers.size() < kMinBufferCountForEviction)) {
                 break;
             }
             auto it = mBuffers.find(*freeIt);

media/bufferpool/2.0/AccessorImpl.h

diff --git a/media/bufferpool/2.0/AccessorImpl.h b/media/bufferpool/2.0/AccessorImpl.h
index cd1b4d0..3d39941 100644
--- a/media/bufferpool/2.0/AccessorImpl.h
+++ b/media/bufferpool/2.0/AccessorImpl.h
@@ -193,6 +193,12 @@
                 : mSizeCached(0), mBuffersCached(0), mSizeInUse(0), mBuffersInUse(0),
                   mTotalAllocations(0), mTotalRecycles(0), mTotalTransfers(0), mTotalFetches(0) {}
 
+            /// # of currently unused buffers
+            size_t buffersNotInUse() const {
+                ALOG_ASSERT(mBuffersCached >= mBuffersInUse);
+                return mBuffersCached - mBuffersInUse;
+            }
+
             /// A new buffer is allocated on an allocation request.
             void onBufferAllocated(size_t allocSize) {
                 mSizeCached += allocSize;

media/bufferpool/2.0/BufferPoolClient.cpp

diff --git a/media/bufferpool/2.0/BufferPoolClient.cpp b/media/bufferpool/2.0/BufferPoolClient.cpp
index 342fef6..9308b81 100644
--- a/media/bufferpool/2.0/BufferPoolClient.cpp
+++ b/media/bufferpool/2.0/BufferPoolClient.cpp
@@ -32,6 +32,8 @@
 static constexpr int64_t kReceiveTimeoutUs = 1000000; // 100ms
 static constexpr int kPostMaxRetry = 3;
 static constexpr int kCacheTtlUs = 1000000; // TODO: tune
+static constexpr size_t kMaxCachedBufferCount = 64;
+static constexpr size_t kCachedBufferCountTarget = kMaxCachedBufferCount - 16;
 
 class BufferPoolClient::Impl
         : public std::enable_shared_from_this<BufferPoolClient::Impl> {
@@ -136,6 +138,10 @@
             --mActive;
             mLastChangeUs = getTimestampNow();
         }
+
+        int cachedBufferCount() const {
+            return mBuffers.size() - mActive;
+        }
     } mCache;
 
     // FMQ - release notifier
@@ -668,10 +674,12 @@
 // should have mCache.mLock
 void BufferPoolClient::Impl::evictCaches(bool clearCache) {
     int64_t now = getTimestampNow();
-    if (now >= mLastEvictCacheUs + kCacheTtlUs || clearCache) {
+    if (now >= mLastEvictCacheUs + kCacheTtlUs ||
+            clearCache || mCache.cachedBufferCount() > kMaxCachedBufferCount) {
         size_t evicted = 0;
         for (auto it = mCache.mBuffers.begin(); it != mCache.mBuffers.end();) {
-            if (!it->second->hasCache() && (it->second->expire() || clearCache)) {
+            if (!it->second->hasCache() && (it->second->expire() ||
+                        clearCache || mCache.cachedBufferCount() > kCachedBufferCountTarget)) {
                 it = mCache.mBuffers.erase(it);
                 ++evicted;
             } else {