Eric Lee / smarc-fsl-linux-kernel

05 Apr, 2016

1 commit

  • 09cbfeaf1   mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros ... Browse Code »

    PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
    ago with promise that one day it will be possible to implement page
    cache with bigger chunks than PAGE_SIZE.

    This promise never materialized. And unlikely will.

    We have many places where PAGE_CACHE_SIZE assumed to be equal to
    PAGE_SIZE. And it's constant source of confusion on whether
    PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
    especially on the border between fs and mm.

    Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
    breakage to be doable.

    Let's stop pretending that pages in page cache are special. They are
    not.

    The changes are pretty straight-forward:

    - << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ;

    - >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ;

    - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};

    - page_cache_get() -> get_page();

    - page_cache_release() -> put_page();

    This patch contains automated changes generated with coccinelle using
    script below. For some reason, coccinelle doesn't patch header files.
    I've called spatch for them manually.

    The only adjustment after coccinelle is revert of changes to
    PAGE_CAHCE_ALIGN definition: we are going to drop it later.

    There are few places in the code where coccinelle didn't reach. I'll
    fix them manually in a separate patch. Comments and documentation also
    will be addressed with the separate patch.

    virtual patch

    @@
    expression E;
    @@
    - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
    + E

    @@
    expression E;
    @@
    - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
    + E

    @@
    @@
    - PAGE_CACHE_SHIFT
    + PAGE_SHIFT

    @@
    @@
    - PAGE_CACHE_SIZE
    + PAGE_SIZE

    @@
    @@
    - PAGE_CACHE_MASK
    + PAGE_MASK

    @@
    expression E;
    @@
    - PAGE_CACHE_ALIGN(E)
    + PAGE_ALIGN(E)

    @@
    expression E;
    @@
    - page_cache_get(E)
    + get_page(E)

    @@
    expression E;
    @@
    - page_cache_release(E)
    + put_page(E)

    Signed-off-by: Kirill A. Shutemov
    Acked-by: Michal Hocko
    Signed-off-by: Linus Torvalds

    Kirill A. Shutemov
     

07 Aug, 2014

1 commit

24 Nov, 2013

1 commit

20 Nov, 2013

1 commit

  • 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