Commits
Chris Mason committed 4ae10b3a133
Btrfs: Add a stripe cache to raid56 The stripe cache allows us to avoid extra read/modify/write cycles by caching the pages we read off the disk. Pages are cached when: * They are read in during a read/modify/write cycle * They are written during a read/modify/write cycle * They are involved in a parity rebuild Pages are not cached if we're doing a full stripe write. We're assuming that a full stripe write won't be followed by another partial stripe write any time soon. This provides a substantial boost in performance for workloads that synchronously modify adjacent offsets in the file, and for the parity rebuild use case in general. The size of the stripe cache isn't tunable (yet) and is set at 1024 entries. Example on flash: dd if=/dev/zero of=/mnt/xxx bs=4K oflag=direct Without the stripe cache -- 2.1MB/s With the stripe cache 21MB/s Signed-off-by: Chris Mason <chris.mason@fusionio.com>