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Chanho Min
2e227ff5e2
The commit 93e72b3c61 ("squashfs: migrate from ll_rw_block usage
to BIO") removed caching of compressed blocks in SquashFS, causing fio
performance regression in workloads with repeated file reads. Without
caching, every read triggers disk I/O, severely impacting performance in
tools like fio.
This patch introduces a new CONFIG_SQUASHFS_COMP_CACHE_FULL Kconfig option
to enable caching of all compressed blocks, restoring performance to
pre-BIO migration levels. When enabled, all pages in a BIO are cached in
the page cache, reducing disk I/O for repeated reads. The fio test
results with this patch confirm the performance restoration:
For example, fio tests (iodepth=1, numjobs=1,
ioengine=psync) show a notable performance restoration:
Disable CONFIG_SQUASHFS_COMP_CACHE_FULL:
IOPS=815, BW=102MiB/s (107MB/s)(6113MiB/60001msec)
Enable CONFIG_SQUASHFS_COMP_CACHE_FULL:
IOPS=2223, BW=278MiB/s (291MB/s)(16.3GiB/59999msec)
The tradeoff is increased memory usage due to caching all compressed
blocks. The CONFIG_SQUASHFS_COMP_CACHE_FULL option allows users to enable
this feature selectively, balancing performance and memory usage for
workloads with frequent repeated reads.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Chanho Min <[email protected]>
Reviewed-by Phillip Lougher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>