Eric Lee / smarc-fsl-linux-kernel

13 Aug, 2020

1 commit

  • d89775fc9   lib/: replace HTTP links with HTTPS ones ... Browse Code »

    Rationale:
    Reduces attack surface on kernel devs opening the links for MITM
    as HTTPS traffic is much harder to manipulate.

    Signed-off-by: Alexander A. Klimov
    Signed-off-by: Andrew Morton
    Acked-by: Coly Li [crc64.c]
    Link: http://lkml.kernel.org/r/20200726112154.16510-1-grandmaster@al2klimov.de
    Signed-off-by: Linus Torvalds

    Alexander A. Klimov
     

16 Aug, 2017

1 commit

  • 5d2405227   lib: Add xxhash module ... Browse Code »

    Adds xxhash kernel module with xxh32 and xxh64 hashes. xxhash is an
    extremely fast non-cryptographic hash algorithm for checksumming.
    The zstd compression and decompression modules added in the next patch
    require xxhash. I extracted it out from zstd since it is useful on its
    own. I copied the code from the upstream XXHash source repository and
    translated it into kernel style. I ran benchmarks and tests in the kernel
    and tests in userland.

    I benchmarked xxhash as a special character device. I ran in four modes,
    no-op, xxh32, xxh64, and crc32. The no-op mode simply copies the data to
    kernel space and ignores it. The xxh32, xxh64, and crc32 modes compute
    hashes on the copied data. I also ran it with four different buffer sizes.
    The benchmark file is located in the upstream zstd source repository under
    `contrib/linux-kernel/xxhash_test.c` [1].

    I ran the benchmarks on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM.
    The VM is running on a MacBook Pro with a 3.1 GHz Intel Core i7 processor,
    16 GB of RAM, and a SSD. I benchmarked using the file `filesystem.squashfs`
    from `ubuntu-16.10-desktop-amd64.iso`, which is 1,536,217,088 B large.
    Run the following commands for the benchmark:

    modprobe xxhash_test
    mknod xxhash_test c 245 0
    time cp filesystem.squashfs xxhash_test

    The time is reported by the time of the userland `cp`.
    The GB/s is computed with

    1,536,217,008 B / time(buffer size, hash)

    which includes the time to copy from userland.
    The Normalized GB/s is computed with

    1,536,217,088 B / (time(buffer size, hash) - time(buffer size, none)).

    | Buffer Size (B) | Hash | Time (s) | GB/s | Adjusted GB/s |
    |-----------------|-------|----------|------|---------------|
    | 1024 | none | 0.408 | 3.77 | - |
    | 1024 | xxh32 | 0.649 | 2.37 | 6.37 |
    | 1024 | xxh64 | 0.542 | 2.83 | 11.46 |
    | 1024 | crc32 | 1.290 | 1.19 | 1.74 |
    | 4096 | none | 0.380 | 4.04 | - |
    | 4096 | xxh32 | 0.645 | 2.38 | 5.79 |
    | 4096 | xxh64 | 0.500 | 3.07 | 12.80 |
    | 4096 | crc32 | 1.168 | 1.32 | 1.95 |
    | 8192 | none | 0.351 | 4.38 | - |
    | 8192 | xxh32 | 0.614 | 2.50 | 5.84 |
    | 8192 | xxh64 | 0.464 | 3.31 | 13.60 |
    | 8192 | crc32 | 1.163 | 1.32 | 1.89 |
    | 16384 | none | 0.346 | 4.43 | - |
    | 16384 | xxh32 | 0.590 | 2.60 | 6.30 |
    | 16384 | xxh64 | 0.466 | 3.30 | 12.80 |
    | 16384 | crc32 | 1.183 | 1.30 | 1.84 |

    Tested in userland using the test-suite in the zstd repo under
    `contrib/linux-kernel/test/XXHashUserlandTest.cpp` [2] by mocking the
    kernel functions. A line in each branch of every function in `xxhash.c`
    was commented out to ensure that the test-suite fails. Additionally
    tested while testing zstd and with SMHasher [3].

    [1] https://phabricator.intern.facebook.com/P57526246
    [2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/XXHashUserlandTest.cpp
    [3] https://github.com/aappleby/smhasher

    zstd source repository: https://github.com/facebook/zstd
    XXHash source repository: https://github.com/cyan4973/xxhash

    Signed-off-by: Nick Terrell
    Signed-off-by: Chris Mason

    Nick Terrell