Re: Guile + Boehm GC: First Remarks

[ludo@chbouib.org (Ludovic Courtès)]

Hi,

I'm finally getting back to this (sorry for the delay!).

Han-Wen Nienhuys <hanwen@xs4all.nl> writes:

> I've patched it a bit to use GC_typed alloc for tagged data. It
> probably doesn't make much of a difference, since 90% of the data is
> regular cells, but see
> http://www.xs4all.nl/~hanwen/public/software/guile-bgc.patch
>
> With the tree benchmark (included in patch, I get 54 secs (Guile 1.8)
> vs. 1:25 (typed BGC). I forgot to measure regular BGC, though.

Thanks for the patch.  I tried it out but it doesn't apparently yield
any performance improvement (see below).

> Note that BGC has ALL_INTERIOR_POINTERS switched on by default
> nowadays, which means that it may scan too much. You could try
> switching that off.

Good idea.  I tried this (patch available in my Arch branch) and it does
indeed yield a slight improvement.  Here's the summary of the various
performance measurements, each time running the whole `gcbench.scm' that
you provided:

  * Guile 1.8					52 sec. (+0%)

  * GBGC w/ tagged allocs			1"27 (+40%)

  * GBGC w/o tagged allocs			1"18 (+33%)

  * GBGC + no interior pointers			1"13 (+29%)

  * GBGC + no interior ptrs + `GC_expand_hp'	1"13 (+29%)

In the last case, `GC_expand_hp ()' is systematically used to increase
the initial heap size at startup time; this may have a positive impact
on short-lived programs, but doesn't have any impact here,
understandably.

I guess we need other bright ideas.  ;-)

Thanks,
Ludovic.



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