[pacman-dev] [PATCH] pkgdelta: Use high compression options offered by xdelta3

[Allan McRae]

On 31/12/14 01:14, Mohammad Alsaleh wrote:
>  * Add -9 which is the highest compression level.
>  * Use lzma for secondary compression.

I believe I said a patch adding '-9 -S djw' would be accepted in the
last discussion of this.

How does lzma for secondary compression compare to djw in terms of
memory footprint and speed?

> 
>  Decompression speed is largely unaffected as most cycles are consumed
>  by xz for re-compression.
> 
>  Some numbers:
> 
>  clang x86_64 [3.5.0-2.1 to 3.5.0-3]
>  17.21MiB      default      (0.73)
>  15.67MiB      -9           (0.67)
>  13.59MiB      -9 -S djw    (0.58)
>  12.01MiB      -9 -S lzma   (0.51)
> 
>  inkscape x86_64 [0.48.5-3 to 0.48.5-4]
>  02.69MiB      default      (0.21)
>  01.64MiB      -9           (0.13)
>  01.30MiB      -9 -S djw    (0.10)
>  01.01MiB      -9 -S lzma   (0.08)
> 
> Signed-off-by: Mohammad Alsaleh <CE.Mohammad.AlSaleh at gmail.com>
> ---
>  scripts/pkgdelta.sh.in | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/pkgdelta.sh.in b/scripts/pkgdelta.sh.in
> index be49326..fe63974 100644
> --- a/scripts/pkgdelta.sh.in
> +++ b/scripts/pkgdelta.sh.in
> @@ -140,7 +140,7 @@ create_xdelta()
>  	deltafile=$(dirname "$newfile")/$pkgname-${oldver}_to_${newver}-$arch.delta
>  	local ret=0
>  
> -	xdelta3 -q -f -s "$oldfile" "$newfile" "$deltafile" || ret=$?
> +	xdelta3 -q -f -9 -S lzma -s "$oldfile" "$newfile" "$deltafile" || ret=$?
>  	if (( ret )); then
>  		error "$(gettext "Delta could not be created.")"
>  		return 1
>