Eric Lee / smarc-fsl-linux-kernel

20 Nov, 2013

2 commits

  • 0d455c12c   Squashfs: Directly decompress into the page cache for file data ... Browse Code »

    This introduces an implementation of squashfs_readpage_block()
    that directly decompresses into the page cache.

    This uses the previously added page handler abstraction to push
    down the necessary kmap_atomic/kunmap_atomic operations on the
    page cache buffers into the decompressors. This enables
    direct copying into the page cache without using the slow
    kmap/kunmap calls.

    The code detects when multiple threads are racing in
    squashfs_readpage() to decompress the same block, and avoids
    this regression by falling back to using an intermediate
    buffer.

    This patch enhances the performance of Squashfs significantly
    when multiple processes are accessing the filesystem simultaneously
    because it not only reduces memcopying, but it more importantly
    eliminates the lock contention on the intermediate buffer.

    Using single-thread decompression.

    dd if=file1 of=/dev/null bs=4096 &
    dd if=file2 of=/dev/null bs=4096 &
    dd if=file3 of=/dev/null bs=4096 &
    dd if=file4 of=/dev/null bs=4096

    Before:

    629145600 bytes (629 MB) copied, 45.8046 s, 13.7 MB/s

    After:

    629145600 bytes (629 MB) copied, 9.29414 s, 67.7 MB/s

    Signed-off-by: Phillip Lougher
    Reviewed-by: Minchan Kim

    Phillip Lougher
     
  • 846b730e9   Squashfs: Generalise paging handling in the decompressors ... Browse Code »

    Further generalise the decompressors by adding a page handler
    abstraction. This adds helpers to allow the decompressors
    to access and process the output buffers in an implementation
    independant manner.

    This allows different types of output buffer to be passed
    to the decompressors, with the implementation specific
    aspects handled at decompression time, but without the
    knowledge being held in the decompressor wrapper code.

    This will allow the decompressors to handle Squashfs
    cache buffers, and page cache pages.

    This patch adds the abstraction and an implementation for
    the caches.

    Signed-off-by: Phillip Lougher
    Reviewed-by: Minchan Kim

    Phillip Lougher