Re: [Qemu-devel] softmmu thoughts

[Magnus Damm <magnus.damm@gmail.com>]

Hello,

Your patch really rocks! I have applied the patch to CVS of today. The
guest OS is custom linux-2.6.9 with serial console. The host is Gentoo
Linux on Pentium M hardware, vanilla 2.6.9 kernel.

Running the guest inside QEMU with 32MiB RAM and -nographic gives me
the following performance gain compared to unpatched CVS of today:

memory index: 40% up
integer index: 36% up
fp index: 2% up

Thanks, keep up the good work!

/ magnus


On Thu, 16 Dec 2004 13:22:41 +0100, Piotras <piotras@gmail.com> wrote:
> Hi!
> 
> I updated the patch to solve problems reported by Jens Arm:
>   * compilation problem on Mandrake 9.1
>   * SEGV problem when working with non-TLS glibc.
> Jens, thanks for your help!
> 
> I also cleaned-up the code and comments in several places (for
> example page_unprotect).
> 
> The patch should apply cleanly to recent CVS. It should work
> with 0.6.1 without problems too.
> 
> 
> Regards,
> 
> Piotrek
> 
> On Tue, 14 Dec 2004 18:54:04 +0100, Piotras <piotras@gmail.com> wrote:
> > Hi!
> >
> > I'm attaching a new patch based on your suggestions. On my machine
> > nbench gives:
> >     memory index: 37% up
> >     integer index: 36% up
> >     fp index: 4% up
> >
> > The patch is divided in three files to simplify review. Part 1 contains
> > mostly rearrangement existing code necessary for the patch. Part 2
> > adds the new mmu mode. Part 3 contains heuristic to optimize
> > performance of iomem and self modifying code.
> >
> > To test the patch create a build directory and run:
> >  > tar -zxf _PATH_TO_qemu-0.6.1.tar.gz
> >  > tar -zxf _PATH_TO_linux-test-0.5.1.tar.gz
> >  > cd qemu-0.6.1
> >  > ./configure --target-list=i386-softmmu
> >  > gunzip < _PATH_TO_mmu-part1.patch.gz | patch -p1
> >  > gunzip < _PATH_TO_mmu-part2.patch.gz | patch -p1
> >  > gunzip < _PATH_TO_mmu-part3.patch.gz | patch -p1
> >  > make
> >  > ./i386-softmmu/qemu -m 64 -L pc-bios -hda ../linux-test/linux.img
> >
> > Last but not least. I'd like to acknowledge Magnus contribution -- VM
> > setup code is derived from his work.
> >
> > Regards,
> >
> > Piotrek
> >
> > On Wed, 20 Oct 2004 14:41:42 +0200, Fabrice Bellard <fabrice@bellard.org> wrote:
> > > Hi,
> > >
> > > The idea is interesting. Here are several suggestions:
> > >
> > > - It would be more efficient and simpler to map one 4KB host memory page
> > > every 8 KB. Then you can have a fixed mmap() mapping (no syscall
> > > overhead to change the mappings) and a simple way to handle unaligned
> > > accesses.
> > > - The critical point would be to keep standard soft MMU accesses for
> > > device access. An architectural change is needed to do that, but it
> > > seems easy to add.
> > > - This patch should work with qemu, not qemu-fast. The future of
> > > qemu-fast is to use a kernel module to have near native performances. It
> > > is not worthwhile to invest time in soft MMU or dynamic translation when
> > > you can just execute the code as is !
> > >
> > > Fabrice.
> 
> 
>