Date: Tue, 28 Mar 2006 09:07:14 +0300 From: Vasil Dimov <vd@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: Robert Watson <rwatson@freebsd.org>, Jason Evans <jasone@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: Proposed addition of malloc_size_np() Message-ID: <20060328060714.GB97222@qlovarnika.bg.datamax> In-Reply-To: <200603271520.11381.jhb@freebsd.org> References: <44247DF1.8000002@FreeBSD.org> <200603271110.02917.jhb@freebsd.org> <44281421.3060401@FreeBSD.org> <200603271520.11381.jhb@freebsd.org>
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On Mon, Mar 27, 2006 at 03:20:08PM -0500, John Baldwin wrote:
> On Monday 27 March 2006 11:34, Jason Evans wrote:
[...]
> > 4) Porting code from Linux. Case in point: Xara Xtreme, currently bein=
g=20
> > ported by Vasil Dimov. At the moment, he has to use dlmalloc.
>=20
> Does it contain a G/C of its own or some such?
>=20
Here is what malloc_usable_size() is used for in Xara Xtreme:
* They keep track of how much (heap) memory is available. Maybe they
support an option like "do not use more that N MiB". This is achieved
by a wrappers to realloc() and free() which manipulate a global?
variable AvailableRAM - the realloc() wrapper decreases AvailableRAM
with (newsize - oldsize) where oldsize is retrieved with
malloc_usable_size(). The free() wrapper increases AvailableRAM with
what is returned by malloc_usable_size().
* Debugging purposes like keeping track of how much memory they
allocated, the filename and linenumber of the allocation
* They use a function similar to realloc(), but which receives the
number of bytes they need to increment the buffer with, rather than
the new size, so they call realloc(p,increment+malloc_usable_size(p))
* A lot of other miscellaneous purposes where they should really keep
track of how many bytes they requested from malloc() rather than
calling malloc_usable_size().
--=20
Vasil Dimov
gro.DSBeerF@dv
Testing can show the presence of bugs, but not their absence.
-- Edsger W. Dijkstra
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