Re: serious (5x) link-time regression in 3.3.5-12 on ia64
according to the changelog, nothing really has changed ... CCing to
the ia64 list.
Duraid Madina writes:
> Hi Mathias, Gerhard and others,
>
> I want to report a nasty performance regression in 3.3.5-12. Moving
> from:
>
> gcc version 3.3.5 (Debian 1:3.3.5-11)
>
> to:
>
> gcc version 3.3.5 (Debian 1:3.3.5-12)
>
> leads to a large reduction in C++ software build speeds, due to
> something that apparently makes 'ld' spend much, much more time than it
> previously did. I reproduced this problem going backwards and forwards
> between these versions by commands like:
>
> dpkg -i g++-3.3_3.3.5-11_ia64.deb gcc-3.3-base_3.3.5-11_ia64.deb gcc-3.3_3.3.5-11_ia64.deb
>
> so, as far as I understand, neither libstdc++ nor binutils changed.
>
> How bad is the problem? Trying to build the LLVM compiler suite,
> (say, version 1.4 from http://llvm.cs.uiuc.edu/releases/ ) on a 2-way IA64
> system with a simple ./configure; time make -j2 with gcc 3.3.5-11 gives:
>
> real 1048.03
> user 1979.93
> sys 54.37
>
> but with gcc 3.3.5-12 gives:
>
> real 1641.14
> user 3037.64
> sys 49.62
>
> Nasty! The build takes 60% longer with 3.3.5-12, and while I haven't
> timed it accurately, the time spent in linking has _greatly_ increased, by a
> factor of at least 5x, perhaps 10x. LLVM is fairly "normal" and portable
> C++, though it is a large source base. (not quite mozilla-sized, though)
>
> Unfortunately, build times from (gcc version 3.4.4 20050314
> (prerelease) (Debian 3.4.3-12)) are more or less the same as those of
> 3.3.5-12, i.e. slow. Again, components of LLVM take literally minutes to
> link on a rather snappy Itanium system. I have not tested older versions of
> 3.4 to see if these too have the performance regression from 3.3.5-11.
>
> I would appreciate it if you could bring this to the attention of
> the relevant people, and I hope I'm posting this in the right place! If
> anyone wants an even more painless way of reproducing this problem, please
> contact me and I will provide a tarball that you can simply unpack,
> configure, make. I'd also appreciate it if someone could confirm exactly
> what has changed between the 3.3.5-11 and 3.3.5-12 packages of gcc, gcc-base
> and g++. diffing gcc-3.3_3.3.5-11.diff and gcc-3.3_3.3.5-12.diff, I can't
> see anything obviously responsible for this regression, so I wonder if
> perhaps some sort of changed environment on whatever machine built
> gcc-3.3.5-12 might be responsible for this regression.
>
> Finally, note that this is all on ia64. I imagine it is likely that
> this regression is platform specific, but the only Debian systems I have
> ready access to are ia64 ones, so I can't test this.
>
> Many thanks in advance,
>
> Duraid
>
>
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