This patch adds an option to set the device block size used to 4K. By default Squashfs sets the device block size (sb_min_blocksize) to 1K or the smallest block size supported by the block device (if larger). This, because blocks are packed together and unaligned in Squashfs, should reduce latency. This, however, gives poor performance on MTD NAND devices where the optimal I/O size is 4K (even though the devices can support smaller block sizes). Using a 4K device block size may also improve overall I/O performance for some file access patterns (e.g. sequential accesses of files in filesystem order) on all media. Signed-off-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx> --- fs/squashfs/Kconfig | 22 ++++++++++++++++++++++ fs/squashfs/squashfs_fs.h | 7 +++++++ fs/squashfs/super.c | 2 +- 3 files changed, 30 insertions(+), 1 deletions(-) diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig index 7797218..d383dd2 100644 --- a/fs/squashfs/Kconfig +++ b/fs/squashfs/Kconfig @@ -66,6 +66,28 @@ config SQUASHFS_XZ If unsure, say N. +config SQUASHFS_4K_DEVBLK_SIZE + bool "Use 4K device block size?" + depends on SQUASHFS + help + By default Squashfs sets the dev block size (sb_min_blocksize) + to 1K or the smallest block size supported by the block device + (if larger). This, because blocks are packed together and + unaligned in Squashfs, should reduce latency. + + This, however, gives poor performance on MTD NAND devices where + the optimal I/O size is 4K (even though the devices can support + smaller block sizes). + + Using a 4K device block size may also improve overall I/O + performance for some file access patterns (e.g. sequential + accesses of files in filesystem order) on all media. + + Setting this option will force Squashfs to use a 4K device block + size by default. + + If unsure, say N. + config SQUASHFS_EMBEDDED bool "Additional option for memory-constrained systems" depends on SQUASHFS diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h index b4a4e53..e8e1464 100644 --- a/fs/squashfs/squashfs_fs.h +++ b/fs/squashfs/squashfs_fs.h @@ -36,6 +36,13 @@ #define SQUASHFS_FILE_SIZE 131072 #define SQUASHFS_FILE_LOG 17 +/* default size of block device I/O */ +#ifdef CONFIG_SQUASHFS_4K_DEVBLK_SIZE +#define SQUASHFS_DEVBLK_SIZE 4096 +#else +#define SQUASHFS_DEVBLK_SIZE 1024 +#endif + #define SQUASHFS_FILE_MAX_SIZE 1048576 #define SQUASHFS_FILE_MAX_LOG 20 diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c index 7438850..2da1715 100644 --- a/fs/squashfs/super.c +++ b/fs/squashfs/super.c @@ -95,7 +95,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent) } msblk = sb->s_fs_info; - msblk->devblksize = sb_min_blocksize(sb, BLOCK_SIZE); + msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); mutex_init(&msblk->read_data_mutex); -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
