[m-dev.] boehm gc USE_MUNMAP

[Julien Fischer]

On Fri, 18 Jan 2008, Peter Wang wrote:

> We're seeing (probably) heap fragmentation leading to unexpectedly large
> heaps for a particular application.  Following the Boehm GC
> documentation, I linked it against a copy of libgc built with the
> USE_MUNMAP option which lets it return unused pages to the OS.
> It solved the problem with that application.
>
> The following speed test on saturn shows a ~20% slow down with this
> option, so I assume we wouldn't want it on by default.  However, we
> could add it as a new grade component, say gc_unmap.  I think it would
> be generally useful.

I'm not exactly thrilled about the prospect of adding yet-another-grade,
but since these things are easier to use when you can install two
versions of the library concurrently, e.g. asm_fast.gc and
asm_fast.gc_unmap, I don't have any objections to adding an new
grade component.

Julien.
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