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List: busybox
Subject: Re: [PATCH] gzip: add support for compression levels 4-9
From: Denys Vlasenko <vda.linux () googlemail ! com>
Date: 2015-04-26 12:23:33
Message-ID: CAK1hOcP67+vOmNMEuFEHuAxqV=9dozW4nrggL9PRKD2soPj05w () mail ! gmail ! com
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Applied, thanks!
On Fri, Apr 24, 2015 at 7:41 PM, Aaro Koskinen <aaro.koskinen@iki.fi> wrote:
> Add support for compression levels 4-9.
>
> function old new delta
> gzip_main 191 306 +115
> usage_messages 40461 40504 +43
> pack_gzip 1924 1907 -17
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 2/1 up/down: 158/-17) Total: 141 bytes
>
> The rationale for this feature is that the current hardcoded 9 level
> is painfully slow with big files. Below are some examples when
> compressing a rootfs tarball (368.9M uncompressed) with different levels
> (gzip 1.6 compression time for comparison in parenthesis):
>
> compression time compressed size
> Without the patch: 1m22.534s 152.0M
> With the patch, 9: 1m15.351s (1m7.419s) 152.0M (old bb default level)
> 8: 0m46.763s (0m43.335s) 152.1M
> 7: 0m28.519s (0m27.076s) 152.4M
> 6: 0m22.960s (0m21.879s) 152.8M (gzip default level)
> 5: 0m16.058s (0m14.740s) 153.9M
> 4: 0m12.484s (0m11.167s) 156.4M
>
> If the compression level support is enabled, we make 6 the default
> as with gzip 1.6.
>
> Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> ---
> archival/gzip.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/archival/gzip.c b/archival/gzip.c
> index bc1f9c6..e6161e2 100644
> --- a/archival/gzip.c
> +++ b/archival/gzip.c
> @@ -62,14 +62,26 @@ aa: 85.1% -- replaced with aa.gz
> //config: 1: larger buffers, larger hash-tables
> //config: 2: larger buffers, largest hash-tables
> //config: Larger models may give slightly better compression
> +//config:
> +//config:config FEATURE_GZIP_LEVELS
> +//config: bool "Enable compression levels"
> +//config: default y
> +//config: depends on GZIP
> +//config: help
> +//config: Enable support for compression levels 4-9. The default level
> +//config: is 6 (without this option 9). If levels 1-3 are specified, 4
> +//config: is used.
>
> //applet:IF_GZIP(APPLET(gzip, BB_DIR_BIN, BB_SUID_DROP))
> //kbuild:lib-$(CONFIG_GZIP) += gzip.o
>
> //usage:#define gzip_trivial_usage
> -//usage: "[-cfd] [FILE]..."
> +//usage: "[-cfd" IF_FEATURE_GZIP_LEVELS("123456789") "] [FILE]..."
> //usage:#define gzip_full_usage "\n\n"
> //usage: "Compress FILEs (or stdin)\n"
> +//usage: IF_FEATURE_GZIP_LEVELS(
> +//usage: "\n -1..9 Compression level"
> +//usage: )
> //usage: "\n -d Decompress"
> //usage: "\n -c Write to stdout"
> //usage: "\n -f Force"
> @@ -252,6 +264,8 @@ enum {
> * input file length plus MIN_LOOKAHEAD.
> */
>
> +#ifndef ENABLE_FEATURE_GZIP_LEVELS
> +
> max_chain_length = 4096,
> /* To speed up deflation, hash chains are never searched beyond this length.
> * A higher limit improves compression ratio but degrades the speed.
> @@ -283,11 +297,23 @@ enum {
> * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
> * meaning.
> */
> +#endif /* ENABLE_FEATURE_GZIP_LEVELS */
> };
>
>
> struct globals {
>
> +#ifdef ENABLE_FEATURE_GZIP_LEVELS
> + unsigned _max_chain_length;
> + unsigned _max_lazy_match;
> + unsigned _good_match;
> + unsigned _nice_match;
> +#define max_chain_length (G1._max_chain_length)
> +#define max_lazy_match (G1._max_lazy_match)
> +#define good_match (G1._good_match)
> +#define nice_match (G1._nice_match)
> +#endif /* ENABLE_FEATURE_GZIP_LEVELS */
> +
> lng block_start;
>
> /* window position at the beginning of the current output block. Gets
> @@ -2161,6 +2187,22 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
> #endif
> {
> unsigned opt;
> +#ifdef ENABLE_FEATURE_GZIP_LEVELS
> + unsigned level;
> + const struct {
> + unsigned char good;
> + unsigned char chain_shift;
> + unsigned short lazy;
> + unsigned short nice;
> + } gzip_level_config[6] = {
> + {4, 4, 4, 16}, /* Level 4 */
> + {8, 5, 16, 32}, /* Level 5 */
> + {8, 7, 16, 128}, /* Level 6 */
> + {8, 8, 32, 128}, /* Level 7 */
> + {32, 10, 128, 258}, /* Level 8 */
> + {32, 12, 258, 258}, /* Level 9 */
> + };
> +#endif /* ENABLE_FEATURE_GZIP_LEVELS */
>
> #if ENABLE_FEATURE_GZIP_LONG_OPTIONS
> applet_long_options = gzip_longopts;
> @@ -2171,6 +2213,11 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
> if (opt & 0x18) // -d and/or -t
> return gunzip_main(argc, argv);
> #endif
> +#ifdef ENABLE_FEATURE_GZIP_LEVELS
> + /* Map 1..3 to 4 and make 6 a default. */
> + level = ffs(opt >> (4 + IF_GUNZIP(2)) & 0x1ff);
> + level = !level ? 6 : MAX(4, level);
> +#endif /* ENABLE_FEATURE_GZIP_LEVELS */
> option_mask32 &= 0x7; /* ignore -q, -0..9 */
> //if (opt & 0x1) // -c
> //if (opt & 0x2) // -f
> @@ -2180,6 +2227,13 @@ int gzip_main(int argc UNUSED_PARAM, char **argv)
> SET_PTR_TO_GLOBALS((char *)xzalloc(sizeof(struct globals)+sizeof(struct globals2))
> + sizeof(struct globals));
>
> +#ifdef ENABLE_FEATURE_GZIP_LEVELS
> + max_chain_length = 1 << gzip_level_config[level - 4].chain_shift;
> + good_match = gzip_level_config[level - 4].good;
> + max_lazy_match = gzip_level_config[level - 4].lazy;
> + nice_match = gzip_level_config[level - 4].nice;
> +#endif /* ENABLE_FEATURE_GZIP_LEVELS */
> +
> /* Allocate all global buffers (for DYN_ALLOC option) */
> ALLOC(uch, G1.l_buf, INBUFSIZ);
> ALLOC(uch, G1.outbuf, OUTBUFSIZ);
> --
> 2.3.3
>
> _______________________________________________
> busybox mailing list
> busybox@busybox.net
> http://lists.busybox.net/mailman/listinfo/busybox
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