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Re: Guile + Boehm GC: First Remarks

From: Ludovic Courtès
Subject: Re: Guile + Boehm GC: First Remarks
Date: Sun, 26 Nov 2006 19:48:20 +0100
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux)


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

Han-Wen Nienhuys <address@hidden> 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
> 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,

I guess we need other bright ideas.  ;-)


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