various optimizations (#704)

- Improvement: Validate chunk hashes when dechunking files in oplog import
- Improvement: Use stream decompression when dechunking files
- Improvement: When assembling blocks for oplog export, make sure we keep under/at block size limit
- Improvement: Make cancelling of oplog import more responsive
- Improvement: Use decompress to composite to avoid allocating a new memory buffer for uncompressed chunks during oplog import
- Improvement: Reduce memory buffer size and allocate it on demand when writing multiple chunks to block store
- Improvement: Reduce lock contention when fetching/checking existence of chunks in block store

1 files changed, 6 insertions, 4 deletions

diff --git a/src/zenstore/compactcas.cpp b/src/zenstore/compactcas.cpp
index a5de5c448..37a8c36b8 100644
--- a/src/zenstore/compactcas.cpp
+++ b/src/zenstore/compactcas.cpp
@@ -301,13 +301,14 @@ CasContainerStrategy::FindChunk(const IoHash& ChunkHash)
 {
 	ZEN_TRACE_CPU("CasContainer::FindChunk");
 
-	RwLock::SharedLockScope _(m_LocationMapLock);
+	RwLock::SharedLockScope Lock(m_LocationMapLock);
 	auto					KeyIt = m_LocationMap.find(ChunkHash);
 	if (KeyIt == m_LocationMap.end())
 	{
 		return IoBuffer();
 	}
-	const BlockStoreLocation& Location = m_Locations[KeyIt->second].Get(m_PayloadAlignment);
+	const BlockStoreLocation Location = m_Locations[KeyIt->second].Get(m_PayloadAlignment);
+	Lock.ReleaseNow();
 
 	IoBuffer Chunk = m_BlockStore.TryGetChunk(Location);
 	return Chunk;
@@ -316,10 +317,11 @@ CasContainerStrategy::FindChunk(const IoHash& ChunkHash)
 bool
 CasContainerStrategy::HaveChunk(const IoHash& ChunkHash)
 {
-	RwLock::SharedLockScope _(m_LocationMapLock);
+	RwLock::SharedLockScope Lock(m_LocationMapLock);
 	if (auto KeyIt = m_LocationMap.find(ChunkHash); KeyIt != m_LocationMap.end())
 	{
-		const BlockStoreLocation& Location = m_Locations[KeyIt->second].Get(m_PayloadAlignment);
+		const BlockStoreLocation Location = m_Locations[KeyIt->second].Get(m_PayloadAlignment);
+		Lock.ReleaseNow();
 		return m_BlockStore.HasChunk(Location);
 	}
 	return false;