Re: Aligned blocks management: obsolete?

[Dmitry Antipov]

On 06/20/2012 09:10 PM, Eli Zaretskii wrote:

> > From: Dmitry Antipov <address@hidden>
> > CC: Paul Eggert <address@hidden>, Eli Zaretskii <address@hidden>,
> >   Emacs development discussions <address@hidden>
> >
> > For example, attached code checks whether memalign tends to create holes
> > while allocating (1024 - 8) blocks aligned at 1024-bytes boundary; optimal
> > pad (BLOCK_PADDING in current code) may be detected with the similar way.
>
> Is it possible to incorporate such tests into Emacs, and write some
> Lisp to execute the tests and report the results?

Such a test can be embedded into configure script.  Moreover, I believe
it might be applicable outside of Emacs; IMHO, it would be nice to have
such a test as a part of gnulib.

> I'm asking because it's hard to use this test as-is on MS-Windows,
> since all of the related functions used by the Windows build are
> reimplemented by Emacs sources, they are not in any system library,
> and so linking a stand-alone test program is not easy.

Previous discussions shows my incompetence in Windows-related areas of
Emacs development, so I have no ideas.

> P.S. If memory fragmentation is what you worry about, then doesn't
> ralloc.c free us from this, on platforms that use it?

I don't know how ralloc.c works.  In general, I believe moving/compacting
GC is the only way to reduce fragmentation; since current design makes it
impossible to move/compact Lisp objects, any underlying allocator can't
really help to reduce fragmentation.

As for the lisp_align_{malloc,free}, this cleanup was designed just because
I have some experimental mmap stuff and want to make some simplifications
before introducing even more complexities :-).

Dmitry

lisp_align_malloc_cleanup.patch
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