Re: Performance issue of libtool-2.4.4

[Richard Purdie]

On Mon, 2015-02-09 at 10:45 +0800, Robert Yang wrote:
> On 02/06/2015 10:46 PM, Bob Friesenhahn wrote:
> > On Fri, 6 Feb 2015, Robert Yang wrote:
> >
> >>
> >>
> >> On 02/06/2015 12:12 PM, Bob Friesenhahn wrote:
> >>> I am not seeing quite the difference between libtool releases that you are
> >>> although I see a big slowdown starting with 2.4.3.  These timings are for
> >>> optimized builds of GraphicsMagick on a 12-core GNU/Linux system using -j 
> >>> 12:
> >>
> >> I think that we can't see obviously slowdown by "make -jN",
> >> but "make -j1" will. And bash is much slower than dash, I'm trying to
> >> figure out why.
> >
> > It seems like this issue is already corrected in the source tree but you are
> 
> Yes, I think that the git repo has fixed the problem:
> 
> commit 408cfb9c5fa8a666917167ffb806cb19deded429
> Author: Gary V. Vaughan <address@hidden>
> Date:   Fri Feb 6 12:58:34 2015 +0000
> 
>      libtool: don't execute automake and autoconf on every invocation.

In an effort to get to the bottom of this I made a git bisection, timing
the performance of building xz with make -j1 using each different
libtool.

The issues come down to this commit:

http://git.savannah.gnu.org/cgit/libtool.git/commit/?id=0a42997c6032b9550a009a271552e811bfbcc430

libtool: rewritten over funclib.sh instead of general.m4sh.

Before that, I get a time of about 20s, after it, 39s. If I cherry-pick
in the fix in master mentioned above, I get 27s.

So whilst things are better (thanks!), the above change is still causing
a regression in the performance somewhere else. Any ideas what else in
that rather large change may be causing this?

Cheers,

Richard