[IMPROVED] Increase cache invalidation times for mb.cache.buf and mb.fss. (#5568)

This is to avoid thrashing on sparse streams and streams that hit max
msgs limits where we have to remove the first that nay be in a totally
different block.

Signed-off-by: Derek Collison <[email protected]>

Author: derekcollison

server/filestore.go

@@ -295,13 +295,13 @@ const (
 	// Maximum size of a write buffer we may consider for re-use.
 	maxBufReuse = 2 * 1024 * 1024
 	// default cache buffer expiration
-	defaultCacheBufferExpiration = 2 * time.Second
+	defaultCacheBufferExpiration = 10 * time.Second
 	// default sync interval
 	defaultSyncInterval = 2 * time.Minute
 	// default idle timeout to close FDs.
 	closeFDsIdle = 30 * time.Second
 	// default expiration time for mb.fss when idle.
-	defaultFssExpiration = 10 * time.Second
+	defaultFssExpiration = 2 * time.Minute
 	// coalesceMinimum
 	coalesceMinimum = 16 * 1024
 	// maxFlushWait is maximum we will wait to gather messages to flush.