reduce lock time for memcache trim (#171)

- Improvement: Faster memcache trimming
  - Reduce calculations while holding bucket lock for memcache trim analysis to reduce contention
  - When trimming memcache, evict 25% more than required to reduce frequency of trimming
  - When trimming memcache, don't repack memcache data vector, defer that to regular garbage collection
  - When trimming memcache, deallocate memcache buffers when not holding exclusive lock in bucket

1 files changed, 4 insertions, 3 deletions

diff --git a/src/zenstore/include/zenstore/cache/cachedisklayer.h b/src/zenstore/include/zenstore/cache/cachedisklayer.h
index 8e31d3222..6d85e8039 100644
--- a/src/zenstore/include/zenstore/cache/cachedisklayer.h
+++ b/src/zenstore/include/zenstore/cache/cachedisklayer.h
@@ -420,7 +420,7 @@ public:
 		}
 		static inline uint64_t EstimateMemCachePayloadMemory(uint64_t PayloadSize)
 		{
-			return sizeof(MemCacheData) + sizeof(IoBufferCore) + RoundUp(PayloadSize, 8u);
+			return sizeof(IoBufferCore) + RoundUp(PayloadSize, 8u);
 		}
 
 		// These locks are here to avoid contention on file creation, therefore it's sufficient
@@ -464,10 +464,11 @@ private:
 			return;
 		}
 
-		MemCacheTrim();
+		StartAsyncMemCacheTrim();
 	}
-	void	 MemCacheTrim();
 	uint64_t MemCacheTrim(std::vector<CacheBucket*>& Buckets, GcClock::TimePoint ExpireTime);
+	bool	 StartAsyncMemCacheTrim();
+	void	 MemCacheTrim();
 
 	GcManager&													  m_Gc;
 	JobQueue&													  m_JobQueue;