Re: [Qemu-devel] Re: memory usage and ioports

[Samuel Thibault <samuel.thibault@eu.citrix.com>]

Paul Brook, le Mon 19 Nov 2007 16:17:26 +0000, a écrit :
> On Monday 19 November 2007, Samuel Thibault wrote:
> > Samuel Thibault, le Mon 19 Nov 2007 15:20:16 +0000, a écrit :
> > > Qemu currently uses 6 65k tables of pointers for handling ioports, which
> > > makes 3MB on 64bit machines. There's a comment that says "XXX: use a two
> > > level table to limit memory usage". But wouldn't it be more simple and
> > > effective to just allocate them through mmap() and when a NULL pointer
> > > is read, call the default handlers?
> >
> > For the ioport_opaque array (500KB on 64bit), it's much simpler, as the
> > attached patch suggests.
> 
> AFAICS This makes absolutely no difference to memory usage.

Ah, sorry, in a unix environment it doesn't indeed.  In an embedded
environment or so which has to provide a fully allocated bss because it
doesn't have cow support early enough, that makes a difference.

Samuel