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Commit 7657cacf authored by Phillip Lougher's avatar Phillip Lougher
Browse files

Squashfs: Add an option to set dev block size to 4K 



This commit 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: default avatarPhillip Lougher <phillip@squashfs.org.uk>
parent c3b92c87

fs/squashfs/Kconfig

+22 −0
Original line number Diff line number Diff line
@@ -78,6 +78,28 @@ 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

fs/squashfs/squashfs_fs.h

+7 −0
Original line number Diff line number Diff line
@@ -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

fs/squashfs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -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);