kot...@apache.org wrote on Tue, 01 Aug 2017 12:18 +0000:
> Author: kotkov
> Date: Tue Aug 1 12:18:23 2017
> New Revision: 1803639
>
> URL: http://svn.apache.org/viewvc?rev=1803639&view=rev
> Log:
> fsfs: Introduce new 'compression' config option.
>
> This option allows explicitly specifying the compression algorithm for
> format 8 repositories. It deprecates the previously used 'compression-level'
> option. The syntax of the new option is:
>
> compression = none | lz4 | zlib | zlib-1 ... zlib-9
Thanks for implementing this, Evgeny. One comment:
> +++ subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c Tue Aug 1 12:18:23 2017
> @@ -947,23 +1052,25 @@ write_config(svn_fs_t *fs,
> "# " CONFIG_OPTION_MAX_LINEAR_DELTIFICATION " = 16"
> NL
> "###"
> NL
> "### After deltification, we compress the data to minimize on-disk size."
> NL
> +"### This setting controls the compression algorithm, which will be used in"
> NL
> +"### future revisions. It can be used to either disable compression or to"
> NL
> +"### select between available algorithms (zlib, lz4). zlib is a general-"
> NL
> +"### purpose compression algorithm. lz4 is a fast compression algorithm"
> NL
> +"### which should be preferred for repositories with large and, possibly,"
> NL
> +"### incompressible files. Note that the compression ratio of lz4 is"
> NL
> +"### usually lower than the one provided by zlib, but using it can"
> NL
> +"### significantly speed up commits as well as reading the data."
> NL
> +"### The syntax of this option is:"
> NL
> +"### " CONFIG_OPTION_COMPRESSION " = none | lz4 | zlib | zlib-1 ...
> zlib-9" NL
> +"### The default value is 'zlib', which is currently equivalent to
> 'zlib-5'." NL
> +"# " CONFIG_OPTION_COMPRESSION " = zlib"
> NL
> +"###"
> NL
> +"### DEPRECATED: The new '" CONFIG_OPTION_COMPRESSION "' option deprecates
> previously used" NL
> +"### '" CONFIG_OPTION_COMPRESSION_LEVEL "' option, which was used to
> configure zlib compression." NL
> +"### For compatibility with previous versions of Subversion, this option
> can"NL
> +"### still be used (and it will result in zlib compression with the"
> NL
> +"### corresponding compression level)."
> NL
> +"### " CONFIG_OPTION_COMPRESSION_LEVEL " = 0 ... 9 (default is 5)"
> NL
The documentation implies that CONFIG_OPTION_COMPRESSION can be used
regardless of the filesystem format, …
> @@ -683,6 +683,60 @@ verify_block_size(apr_int64_t block_size
> +static svn_error_t *
> +parse_compression_option(compression_type_t *compression_type_p,
> + int *compression_level_p,
> + const char *value)
> +{
> @@ -816,6 +859,68 @@ read_config(fs_fs_data_t *ffd,
> {
> ffd->pack_after_commit = FALSE;
> }
> +
> + /* Initialize compression settings in ffd. */
> + if (ffd->format >= SVN_FS_FS__MIN_SVNDIFF2_FORMAT)
> + {
> + svn_config_get(config, &compression_val,
> + CONFIG_SECTION_DELTIFICATION,
> + CONFIG_OPTION_COMPRESSION, NULL);
> + svn_config_get(config, &compression_level_val,
> + CONFIG_SECTION_DELTIFICATION,
> + CONFIG_OPTION_COMPRESSION_LEVEL, NULL);
> + }
> + else if (ffd->format >= SVN_FS_FS__MIN_DELTIFICATION_FORMAT)
> + {
> + SVN_ERR(svn_config_get_int64(config, &compression_level,
> + CONFIG_SECTION_DELTIFICATION,
> + CONFIG_OPTION_COMPRESSION_LEVEL,
> + SVN_DELTA_COMPRESSION_LEVEL_DEFAULT));
… but the code only reads CONFIG_OPTION_COMPRESSION in f8 filesystems.
Given the docs as written, I would expect to be able to edit fsfs.conf
and replace 'compression-level = 4' with 'compression = zlib-4' without
doing an 'svnadmin upgrade'; so I think the SVN_FS_FS__MIN_DELTIFICATION_FORMAT
codepath should honour CONFIG_OPTION_COMPRESSION (and error out if it is
set to "lz4").
Cheers,
Daniel
> + }
> + else if (ffd->format >= SVN_FS_FS__MIN_SVNDIFF1_FORMAT)
> + {
> + ffd->delta_compression_type = compression_type_zlib;
> + ffd->delta_compression_level = SVN_DELTA_COMPRESSION_LEVEL_DEFAULT;
> + }
> + else
> + {
> + ffd->delta_compression_type = compression_type_none;
> + ffd->delta_compression_level = SVN_DELTA_COMPRESSION_LEVEL_NONE;
> + }
> +
> #ifdef SVN_DEBUG
> SVN_ERR(svn_config_get_bool(config, &ffd->verify_before_commit,
> CONFIG_SECTION_DEBUG,
