[gambit-list] The monster that killed gcc

Marc Feeley feeley at iro.umontreal.ca
Mon Mar 19 15:02:49 EDT 2018


I think you should figure out which of the configure options

  --enable-single-host
  --enable-c-opt
  --enable-gcc-opts

are the most useful/beneficial for the kind of code generated by Gerbil.  I suspect that --enable-single-host is the most performance-enhancing option, and --enable-c-opt only gives a marginal speed increase at the cost of a much higher C compile time.

If you do try the various combinations, please report your results here.  I’d like to know if my intuition is correct.

Marc



> On Mar 19, 2018, at 2:56 PM, Dimitris Vyzovitis <vyzo at hackzen.org> wrote:
> 
> My gambit is configured with  --enable-single-host --enable-c-opt --enable-gcc-opts.
> I have 8G on my current laptop, but I run without a swap; the death occurs at around 6G. 
> It's not only the memory usage though, it takes forever too. clang on travis didn't OOM, but it took 15min on the file.
> 
> I think it might be a case of really bad interaction between the various optimizers in the 3 compilers involved. The gerbil emitted code is already heavily optimized to perform match tree linearization (I have a shiny new optimizer that optimizes match and syntax- case expansions).
> That means you can't reasonably inline anything other than single use procedures within the optimized blocks.
> 
> -- vyzo
> 
> 
> On Mon, Mar 19, 2018 at 8:41 PM, Marc Feeley <feeley at iro.umontreal.ca> wrote:
> The default inlining-limit is 350, so the expansion from 100 is quite possible.
> 
> But the problem here is that gcc chokes on the compilation of the C file.  So… what are the compilation options passed to gcc?
> 
> - are you using --enable-single-host ?
> - are you using a higher level of optimization such as -O2 or -O3 rather than the default -O1 ?
> 
> These will definitely increase the pressure on the C compiler.  Also, some versions of gcc do a better job at compiling large C files.  The file lib/_io.c in the Gambit distribution is about 90kloc and I have never gotten an OOM error from gcc while compiling it, even though I use a “make -j 8” (8 C compilations in parallel).  I do have 16 GB of RAM on my machine… how much RAM do you have on yours?
> 
> Marc
> 
> 
> 
> > On Mar 19, 2018, at 2:31 PM, Dimitris Vyzovitis <vyzo at hackzen.org> wrote:
> >
> > It's 140kloc without the inlining declaration and just 22Kloc with the declaration.
> >
> > -- vyzo
> >
> > On Mon, Mar 19, 2018 at 8:27 PM, Marc Feeley <feeley at iro.umontreal.ca> wrote:
> > Out of curiosity, what is the number of LOC of C with and without the inlining-limit?
> >
> > I’m just wondering if this should be classified as an issue, or if the inliner is just doing its work as expected.
> >
> > Marc
> >
> >
> >
> > > On Mar 19, 2018, at 2:23 PM, Dimitris Vyzovitis <vyzo at hackzen.org> wrote:
> > >
> > > It seems it's the inliner going haywire -- if I add a (declare (inlining-limit 100)), then it compiles in 20s.
> > >
> > > -- vyzo
> > >
> > > On Mon, Mar 19, 2018 at 7:29 PM, Dimitris Vyzovitis <vyzo at hackzen.org> wrote:
> > > The attached file results in a 140kloc monster that results in gcc dying with OOM after several minutes of effort, and I would like to understand why.
> > > Any ideas?
> > >
> > > -- vyzo
> > >
> >
> >
> 
> 




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