On Mon, Mar 28, 2016 at 10:05:44AM -0700, Eric Nelson wrote:
Add a block device cache to speed up repeated reads of block devices by various filesystems.
This small amount of cache can dramatically speed up filesystem operations by skipping repeated reads of common areas of a block device (typically directory structures).
This has shown to have some benefit on FAT filesystem operations of loading a kernel and RAM disk, but more dramatic benefits on ext4 filesystems when the kernel and/or RAM disk are spread across multiple extent header structures as described in commit fc0fc50.
The cache is implemented through a minimal list (block_cache) maintained in most-recently-used order and count of the current number of entries (cache_count). It uses a maximum block count setting to prevent copies of large block reads and an upper bound on the number of cached areas.
The maximum number of entries in the cache defaults to 32 and the maximum number of blocks per cache entry has a default of 2, which has shown to produce the best results on testing of ext4 and FAT filesystems.
The 'blkcache' command (enabled through CONFIG_CMD_BLOCK_CACHE) allows changing these values and can be used to tune for a particular filesystem layout.
Signed-off-by: Eric Nelson eric@nelint.com
Applied to u-boot/master, thanks!