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Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to spe
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation? |
Date: |
Mon, 17 Aug 2015 23:08:37 +0200 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On 2015-08-17 18:25, Artyom Tarasenko wrote:
> On Mon, Aug 17, 2015 at 5:40 PM, Richard Henderson <address@hidden> wrote:
> > On 08/17/2015 07:19 AM, Artyom Tarasenko wrote:
> >> Well, on the other hand, every access goes via helper_check_align.
> >> There is a comment /* XXX remove alignment check */.
> >> I wonder how this can be done in a more efficient way?
> >
> > Not ever access does so. There are only 3 memory related calls to
> > check_align.
> > The other three are for indirect branches.
>
> Yes, but I think it's the 3 most used ones.
>
> > For the 8 byte memory operations we can just remove the checks. There, the
> > softmmu operation checks the alignment.
>
> This is a good news. Where does it happen?
>
> > For usermode, we've typically ignored
> > the guest alignment (which also causes failures for a host that requires
> > alignment emulating a guest that does not).
A tiny bit of topic, but couldn't we force the use of unaligned access
load/store instructions in user mode instead? For example in QEMU we
can use the LWL/LWR couple instead of LW. I doubt it will make any
measurable difference in speed. For the MIPS case, that doesn't work
for 16-bit load/stores though.
The best would indeed be to switch to softmmu for the user mode. I know
there are people working on that, but given that it might take time, it
could be a simple temporary solution.
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
address@hidden http://www.aurel32.net
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, (continued)
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/06
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/18
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Aurelien Jarno, 2015/08/18
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/18
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/18
- Message not available
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/19
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/17
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/17
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/27