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

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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: Phillip Lougher <phillip@squashfs.org.uk>
This commit is contained in:
Phillip Lougher
2011-10-22 01:34:48 +01:00
parent c3b92c8787
commit 7657cacf47
3 changed files with 30 additions and 1 deletions
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2
fs/squashfs/super.c
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@@ -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);