Re: [PATCH v2] PM: hibernate: Support to select compression algorithm

[Rafael J. Wysocki]

On Wed, Feb 14, 2024 at 8:40 AM Nikhil V <quic_nprakash@xxxxxxxxxxx> wrote:
>
> Currently the default compression algorithm is selected based on
> compile time options. Introduce a module parameter "hibernate.compressor"
> to override this behaviour.
>
> Different compression algorithms have different characteristics and
> hibernation may benefit when it uses any of these algorithms, especially
> when a secondary algorithm(LZ4) offers better decompression speeds over a
> default algorithm(LZO), which in turn reduces hibernation image restore
> time.
>
> Users can override the default algorithm in two ways:
>  1) Passing "hibernate.compressor" as kernel command line parameter.
>     Usage:
>         LZO: hibernate.compressor=lzo
>         LZ4: hibernate.compressor=lz4
>
>  2) Specifying the algorithm at runtime.
>     Usage:
>         LZO: echo lzo > /sys/module/hibernate/parameters/compressor
>         LZ4: echo lz4 > /sys/module/hibernate/parameters/compressor
>
> Currently LZO and LZ4 are the supported algorithms. LZO is the default
> compression algorithm used with hibernation.
>
> Signed-off-by: Nikhil V <quic_nprakash@xxxxxxxxxxx>
> ---
> This patch is dependent on the patch series, [1] (patches 1/4 to 3/4).
> This is picked in linux-next, [2].
>  [1] https://lore.kernel.org/all/cover.1705927916.git.quic_nprakash@xxxxxxxxxxx/
>  [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/kernel/power?h=next-20240212
>
> Changes in v2:
>  Changes to incorporate suggestions from Randy Dunlap:
>   - Update documentation to specify the default compression algorithm.
>  Link to v1:
>   https://lore.kernel.org/all/3776355f920c1af44490e076072f93bafdf128cc.1707740870.git.quic_nprakash@xxxxxxxxxxx/
>
>  .../admin-guide/kernel-parameters.txt         | 11 ++++
>  kernel/power/hibernate.c                      | 57 ++++++++++++++++++-
>  2 files changed, 65 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 31b3a25680d0..8f7fb911b2cc 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1748,6 +1748,17 @@
>                                 (that will set all pages holding image data
>                                 during restoration read-only).
>
> +       hibernate.compressor=   [HIBERNATION] Compression algorithm to be
> +                               used with hibernation.
> +                               Format: { lzo | lz4 }
> +                               Default: lzo
> +
> +                               lzo: Select LZO compression algorithm to
> +                               compress/decompress hibernation image.
> +
> +                               lz4: Select LZ4 compression algorithm to
> +                               compress/decompress hibernation image.
> +
>         highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
>                         size of <nn>. This works even on boxes that have no
>                         highmem otherwise. This also works to reduce highmem
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 219191d6d0e8..43b1a82e800c 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -47,7 +47,7 @@ dev_t swsusp_resume_device;
>  sector_t swsusp_resume_block;
>  __visible int in_suspend __nosavedata;
>
> -static const char *default_compressor = CONFIG_HIBERNATION_DEF_COMP;
> +static char hibernate_compressor[CRYPTO_MAX_ALG_NAME] = CONFIG_HIBERNATION_DEF_COMP;
>
>  /*
>   * Compression/decompression algorithm to be used while saving/loading
> @@ -748,7 +748,7 @@ int hibernate(void)
>          * Query for the compression algorithm support if compression is enabled.
>          */
>         if (!nocompress) {
> -               strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
> +               strscpy(hib_comp_algo, hibernate_compressor, sizeof(hib_comp_algo));
>                 if (crypto_has_comp(hib_comp_algo, 0, 0) != 1) {
>                         pr_err("%s compression is not available\n", hib_comp_algo);
>                         return -EOPNOTSUPP;
> @@ -999,7 +999,7 @@ static int software_resume(void)
>                 if (swsusp_header_flags & SF_COMPRESSION_ALG_LZ4)
>                         strscpy(hib_comp_algo, COMPRESSION_ALGO_LZ4, sizeof(hib_comp_algo));
>                 else
> -                       strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
> +                       strscpy(hib_comp_algo, COMPRESSION_ALGO_LZO, sizeof(hib_comp_algo));
>                 if (crypto_has_comp(hib_comp_algo, 0, 0) != 1) {
>                         pr_err("%s compression is not available\n", hib_comp_algo);
>                         error = -EOPNOTSUPP;
> @@ -1422,6 +1422,57 @@ static int __init nohibernate_setup(char *str)
>         return 1;
>  }
>
> +static const char * const comp_alg_enabled[] = {
> +#if IS_ENABLED(CONFIG_CRYPTO_LZO)
> +       COMPRESSION_ALGO_LZO,
> +#endif
> +#if IS_ENABLED(CONFIG_CRYPTO_LZ4)
> +       COMPRESSION_ALGO_LZ4,
> +#endif
> +};
> +
> +static int hibernate_compressor_param_set(const char *compressor,
> +               const struct kernel_param *kp)
> +{
> +       unsigned int sleep_flags;
> +       int index, ret;
> +
> +       sleep_flags = lock_system_sleep();
> +
> +       index = sysfs_match_string(comp_alg_enabled, compressor);
> +       if (index >= 0) {
> +               ret = param_set_copystring(comp_alg_enabled[index], kp);
> +               if (!ret)
> +                       strscpy(hib_comp_algo, comp_alg_enabled[index],
> +                               sizeof(hib_comp_algo));
> +       } else {
> +               ret = index;
> +       }
> +
> +       unlock_system_sleep(sleep_flags);
> +
> +       if (ret)
> +               pr_debug("Cannot set specified compressor %s\n",
> +                        compressor);
> +
> +       return ret;
> +}
> +
> +static const struct kernel_param_ops hibernate_compressor_param_ops = {
> +       .set    = hibernate_compressor_param_set,
> +       .get    = param_get_string,
> +};
> +
> +static struct kparam_string hibernate_compressor_param_string = {
> +       .maxlen = sizeof(hibernate_compressor),
> +       .string = hibernate_compressor,
> +};
> +
> +module_param_cb(compressor, &hibernate_compressor_param_ops,
> +               &hibernate_compressor_param_string, 0644);
> +MODULE_PARM_DESC(compressor,
> +                "Compression algorithm to be used with hibernation");
> +
>  __setup("noresume", noresume_setup);
>  __setup("resume_offset=", resume_offset_setup);
>  __setup("resume=", resume_setup);
> --

Applied as 6.9 material, thanks!