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Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to spe
From: |
Artyom Tarasenko |
Subject: |
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation? |
Date: |
Thu, 27 Aug 2015 17:58:07 +0200 |
On Wed, Aug 26, 2015 at 9:47 PM, Richard Henderson <address@hidden> wrote:
> On 08/26/2015 09:17 AM, Artyom Tarasenko wrote:
>>
>> After some debugging I think it's caused by memory faults. On every
>> MMU miss / access fault
>> TB is re-translated multiple times till the faulting instruction is found.
>
>
> That shouldn't happen. Are you certain it's not multiple MMU misses/faults?
You are right. These are multiple faults.
>> AFAICT we produce data/access faults only on load/store instructions, i.e.
>> if GET_FIELD(insn, 0, 1) == 3. Can this knowledge be used to reduce
>> the number of re-translations?
>
>
> No.
>
> From the fault, we have a host address where the fault occured. We then
> retranslate the TB looking for what guest address corresponds to the code
> generated at the host address. This is a one-pass process, not the multiple
> passes you seem to be imagining. It also means we can't skip non-memory
> insns during retranslation, as the host addresses would no longer line up.
Right, thanks for clarifying this. I was confused by the multiple
"Search PC..." messages.
But I see now that one message corresponds to one translated instruction,
not to one translation block. The log message should probably be moved
one level up, and btw it's not sparc-specific, this part seems to be a
copy-pasta in multiple targets.
> That said, sun4u is a software managed tlb, which requires *lots* more extra
> faults than a hardware managed tlb. In the later case, we can perform the
> page table lookup and then continue the memory instruction without faulting.
>
> I think that implementing sun4v, with (most of) the hypervisor actually
> within qemu, is the only way to get good performance for Sparc.
I thought about it. The guest can profit from the knowledge it is executed
virtualized in multiple ways.
The problem with this approach is that Linux/sparc64 is currently not
the primary target OS for me.
And the legacy OSes do not support sun4v. Even a Solaris 8 has a quite
limited support for it.
Artyom
--
Regards,
Artyom Tarasenko
SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu
- 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, 2015/08/21
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/22
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/22
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/22
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/23
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Richard Henderson, 2015/08/22
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/26
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Richard Henderson, 2015/08/26
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/27
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Richard Henderson, 2015/08/27
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?,
Artyom Tarasenko <=
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/20
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Artyom Tarasenko, 2015/08/20
Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/03
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Karel Gardas, 2015/08/03
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/03
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Karel Gardas, 2015/08/06
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/06
- 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?, Karel Gardas, 2015/08/06
- Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?, Dennis Luehring, 2015/08/06