Changeset 130212 in webkit

Timestamp:

Oct 2, 2012, 2:24:19 PM (13 years ago)

Author:

mhahnenberg@apple.com

Message:

Block freeing thread should sleep indefinitely when there's no work to do
​https://bugs.webkit.org/show_bug.cgi?id=98084

Reviewed by Geoffrey Garen.

Currently the block freeing thread wakes up once a second to check if there are any blocks
for it to release back to the OS. This is wasteful. We should change it to sleep when it
realizes there are no more blocks to free. Any thread that returns a block to the BlockAllocator
should then notify the block freeing thread that there is more work to do now.

• heap/BlockAllocator.cpp:

(JSC::BlockAllocator::BlockAllocator):
(JSC::BlockAllocator::blockFreeingThreadMain):

• heap/BlockAllocator.h:

(BlockAllocator):
(JSC::BlockAllocator::deallocate):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• heap/BlockAllocator.cpp (modified) (1 diff)
• heap/BlockAllocator.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2012-10-01  Mark Hahnenberg  <mhahnenberg@apple.com>
+
+        Block freeing thread should sleep indefinitely when there's no work to do
+        https://bugs.webkit.org/show_bug.cgi?id=98084
+
+        Reviewed by Geoffrey Garen.
+
+        Currently the block freeing thread wakes up once a second to check if there are any blocks 
+        for it to release back to the OS. This is wasteful. We should change it to sleep when it 
+        realizes there are no more blocks to free. Any thread that returns a block to the BlockAllocator 
+        should then notify the block freeing thread that there is more work to do now.
+
+        * heap/BlockAllocator.cpp:
+        (JSC::BlockAllocator::BlockAllocator):
+        (JSC::BlockAllocator::blockFreeingThreadMain):
+        * heap/BlockAllocator.h:
+        (BlockAllocator):
+        (JSC::BlockAllocator::deallocate):
+
 2012-10-01  Michael Saboff  <msaboff@apple.com>
 

trunk/Source/JavaScriptCore/heap/BlockAllocator.cpp

@@ -139 +139 @@
             DeadBlock::destroy(block).deallocate();
         }
+
+        // Sleep until there is actually work to do rather than waking up every second to check.
+        MutexLocker locker(m_freeBlockConditionLock);
+        m_freeBlockLock.Lock();
+        while (!m_numberOfFreeBlocks && !m_blockFreeingThreadShouldQuit) {
+            m_freeBlockLock.Unlock();
+            m_freeBlockCondition.wait(m_freeBlockConditionLock);
+            m_freeBlockLock.Lock();
+        }
+        m_freeBlockLock.Unlock();
     }
 }

trunk/Source/JavaScriptCore/heap/BlockAllocator.h

@@ -105 +105 @@
 inline void BlockAllocator::deallocate(PageAllocationAligned allocation)
 {
-    SpinLockHolder locker(&m_freeBlockLock);
-    m_freeBlocks.push(DeadBlock::create(allocation));
-    m_numberOfFreeBlocks++;
+    size_t numberOfFreeBlocks;
+    {
+        SpinLockHolder locker(&m_freeBlockLock);
+        m_freeBlocks.push(DeadBlock::create(allocation));
+        numberOfFreeBlocks = m_numberOfFreeBlocks++;
+    }
+
+    if (!numberOfFreeBlocks) {
+        MutexLocker mutexLocker(m_freeBlockConditionLock);
+        m_freeBlockCondition.signal();
+    }
 }