[m-dev.] boehm gc USE_MUNMAP
Peter Wang
novalazy at gmail.com
Fri Jan 18 16:50:03 AEDT 2008
On 2008-01-18, Julien Fischer <juliensf at csse.unimelb.edu.au> wrote:
>
> 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.
I'm not thrilled at updating the scripts to support another gc grade
either. As it only changes which gc library an application links
against, it would be a real waste to install asm_fast.gc and
asm_fast.gc_unmap -- all the files would be exactly the same.
Maybe the use of libgc_unmap should just be an option passed to mmc or
ml? I don't know how the install process would work though.
Peter
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