bug#20006: Bash-specific performance by avoiding sed

[Pavel Raiskup]

On Friday 09 of October 2015 17:16:03 Pavel Raiskup wrote:
> > Here's a (lightly-tested) idea of what it would look like, where we'd
> > have to audit every caller to deal with the result already including
> > full quoting:
> > 
> > if test yes = `(x=; printf -v x %q yes; echo $x) 2>/dev/null`; then
> >   func_quote()
> >   {
> >     printf -v func_quote_result %q "$1"
> >   }
> > else
> >   func_quote()
> >   {
> >     portable version, except add:
> >     func_quote_result="\"$func_quote_result\""
> >   }
> > fi
> >
> > Note that with this variant, the portable version converts 'a  *"b' into
> > '"a  *\"b"', while the bash version converts it into 'a\ \ \*\"b'.
> 
> Thanks!  I've done a simple testing too .. and it seems to be equivalent
> to '$SED $sed_quote_subst' (in usecases like: string -> quote -> eval).
> 
> Well -- I'm not 100% sure I want to hack this in and risk some issues.  On
> the other hand, I'm able to review the patches if somebody wanted to give
> it a try (the small bash slowdown from v2.4.2 to v2.4.6 is not good
> motivation for me).

Hm, I was thinking thinking about this over the weekend and I wanted to do
some testing before I would definitely reject that idea.  But it sounds
like the printf builtin helps lets say significantly to bash and does not
hurt others.  I changed the function names so the changes to libtool code
should be pretty transparent (even though it is rather large change).

I'm posting results of the performance test (on systemd package) and
attaching 3 "planned to be pushed" patches.  So testing '2.4.2' version
(fast), git-version after applying 0001 and 0002 (patch-2) and including
0003 (patch-3).

The dirname of test is in format 'PACKAGE-SHELL-LTVERSION'.

Pavel
-----

%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-bash-2.4.2)
0:28.50 56.84 41.42
0:28.38 56.72 41.41
0:28.26 56.44 41.68
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-bash-2.4.6.13-f729)
1:06.13 232.12  23.33
1:06.52 232.28  23.35
1:06.54 232.16  23.52
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-bash-2.4.6.14-7a09)
0:46.52 151.16  24.48
0:46.64 150.80  24.60
0:46.69 151.12  23.85


%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-dash-2.4.2)
0:16.34 22.22 28.62
0:17.13 22.57 29.09
0:17.11 22.37 29.24
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-dash-2.4.6.13-f729)
0:23.38 58.80 21.32
0:23.16 58.81 21.16
0:23.21 58.67 21.15
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-dash-2.4.6.14-7a09)
0:21.36 51.20 21.62
0:21.23 50.59 21.76
0:21.25 50.70 21.55


%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-ksh-2.4.2)
0:19.65 30.76 34.12
0:21.09 30.68 34.63
0:19.75 30.83 34.29
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-ksh-2.4.6.13-f729)
0:30.75 85.60 25.41
0:30.70 85.51 25.52
0:30.80 85.65 25.41
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-ksh-2.4.6.14-7a09)
0:30.78 84.25 26.14
0:30.63 83.65 26.17
0:30.62 83.85 26.02


%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-zsh-2.4.2)
0:27.94 44.47 48.97
0:28.03 44.29 49.31
0:28.60 44.48 48.93
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-zsh-2.4.6.13-f729)
0:47.60 140.30  41.70
0:47.53 139.84  41.89
0:47.56 139.71  42.12
%E  %U  %S (/home/praiskup/rh/projects/systemd-perf/systemd-zsh-2.4.6.14-7a09)
0:46.21 131.88  41.72
0:46.62 131.31  42.25
0:46.44 131.35  42.03

0001-libtool-mitigate-the-sed_quote_subst-slowdown.patch
Description: Text Data

0002-libtool-optimizing-options-parser-hooks.patch
Description: Text Data

0003-funclib-refactor-quoting-methods-a-bit.patch
Description: Text Data