On Tue, Oct 30, 2018 at 12:06:21PM -0700, Nick Terrell wrote:
> From: Jennifer Liu <jenniferliu...@fb.com>
>
> Adds zstd compression level support to btrfs. Zstd requires
> different amounts of memory for each level, so the design had
> to be modified to allow set_level() to allocate memory. We
> preallocate one workspace of the maximum size to guarantee
> forward progress. This feature is expected to be useful for
> read-mostly filesystems, or when creating images.
>
> Benchmarks run in qemu on Intel x86 with a single core.
> The benchmark measures the time to copy the Silesia corpus [0] to
> a btrfs filesystem 10 times, then read it back.
>
> The two important things to note are:
> - The decompression speed and memory remains constant.
> The memory required to decompress is the same as level 1.
> - The compression speed and ratio will vary based on the source.
>
> Level Ratio Compression Decompression Compression Memory
> 1 2.59 153 MB/s 112 MB/s 0.8 MB
> 2 2.67 136 MB/s 113 MB/s 1.0 MB
> 3 2.72 106 MB/s 115 MB/s 1.3 MB
> 4 2.78 86 MB/s 109 MB/s 0.9 MB
> 5 2.83 69 MB/s 109 MB/s 1.4 MB
> 6 2.89 53 MB/s 110 MB/s 1.5 MB
> 7 2.91 40 MB/s 112 MB/s 1.4 MB
> 8 2.92 34 MB/s 110 MB/s 1.8 MB
> 9 2.93 27 MB/s 109 MB/s 1.8 MB
> 10 2.94 22 MB/s 109 MB/s 1.8 MB
> 11 2.95 17 MB/s 114 MB/s 1.8 MB
> 12 2.95 13 MB/s 113 MB/s 1.8 MB
> 13 2.95 10 MB/s 111 MB/s 2.3 MB
> 14 2.99 7 MB/s 110 MB/s 2.6 MB
> 15 3.03 6 MB/s 110 MB/s 2.6 MB
>
> [0] http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
Reviewed-by: Omar Sandoval <osan...@fb.com>
> Signed-off-by: Jennifer Liu <jenniferliu...@fb.com>
> Signed-off-by: Nick Terrell <terre...@fb.com>
> ---
> fs/btrfs/compression.c | 172 +++++++++++++++++++++++++----------------
> fs/btrfs/compression.h | 18 +++--
> fs/btrfs/lzo.c | 5 +-
> fs/btrfs/super.c | 7 +-
> fs/btrfs/zlib.c | 33 ++++----
> fs/btrfs/zstd.c | 74 ++++++++++++++----
> 6 files changed, 204 insertions(+), 105 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 2955a4ea2fa8..bd8e69381dc9 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -822,11 +822,15 @@ void __init btrfs_init_compress(void)
>
> /*
> * Preallocate one workspace for each compression type so
> - * we can guarantee forward progress in the worst case
> + * we can guarantee forward progress in the worst case.
> + * Provide the maximum compression level to guarantee large
> + * enough workspace.
> */
> - workspace = btrfs_compress_op[i]->alloc_workspace();
> + workspace = btrfs_compress_op[i]->alloc_workspace(
> + btrfs_compress_op[i]->max_level);
> if (IS_ERR(workspace)) {
> - pr_warn("BTRFS: cannot preallocate compression
> workspace, will try later\n");
> + pr_warn("BTRFS: cannot preallocate compression "
> + "workspace, will try later\n");
Nit: since you didn't change this line, don't rewrap it.
