Re: Garbage collector tuning?

[ludo@gnu.org (Ludovic Courtès)]

Jan Wedekind <jan@wedesoft.de> skribis:

> I wonder whether there is a more performant way to allocate larger
> memory blocks (e.g. 1 MByte). "gc-malloc-pointerless" seems to be much
> slower than "malloc":
>
>                                            user     system      total        real
>     Guile allocate memory              0.003780   0.000020   0.003800 (  0.003810)
>     C allocate memory                  0.000060   0.000000   0.000060 (  0.000070)

It isn’t fair to compare GC_malloc_pointerless with malloc.  Instead, it
should be compared with interleaved malloc + free sequences.

You should find more on this topic on the home page of libgc, the GC
that Guile uses: <http://www.hboehm.info/gc/>

> Is there a way to control how often the garbage collector is run?

The file doc/README.environment in libgc describes some useful
environment variables, notably these:

  GC_INITIAL_HEAP_SIZE=<bytes> -	Initial heap size in bytes.  May speed up
                                  process start-up.

  GC_MAXIMUM_HEAP_SIZE=<bytes> - Maximum collected heap size.

  GC_MARKERS=<n> - Linux w/threads and parallel marker only.  Set the number
                  of marker threads.  This is normally set to the number of
                  processors.  It is safer to adjust GC_MARKERS than GC_NPROCS,
                  since GC_MARKERS has no impact on the lock implementation.

Guile also honors the ‘GC_FREE_SPACE_DIVISOR’ environment variable.  See
the comments in gc.h for the meaning of this one.

HTH,
Ludo’.