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[Qemu-devel] Re: branches are expensive
From: |
Steffen Liebergeld |
Subject: |
[Qemu-devel] Re: branches are expensive |
Date: |
Tue, 17 Mar 2009 11:36:07 +0000 (UTC) |
User-agent: |
slrn/pre0.9.9-111 (Linux) |
Hi Avi,
Avi Kivity <address@hidden> schrieb:
> Steffen Liebergeld wrote:
>> Hi,
>>
>> while measuring the execution of an ARM guest, I encountered that branches
>> are
>> extremely expensive in terms of executed host instructions. A single ARM
>> branch takes 148 to 152 host instructions. In my setup host and guest use the
>> ARM instruction set architecture.
>>
>> My question is what makes branches so expensive? What code is run when
>> executing a branch? Other instructions are translated to 14 to 40
>> instructions.
>>
>
> I'm no tcg guru, but if branches are not chained, you'd need an
> expensive lookup to find the next translation block. If branches are
> chained they'll probably be much faster.
Sure. But how can I get to know how many TBs are chained.
Greetings, Steffen
- [Qemu-devel] Re: branches are expensive, (continued)
- [Qemu-devel] Re: branches are expensive, Jan Kiszka, 2009/03/17
- [Qemu-devel] Re: branches are expensive, Steffen Liebergeld, 2009/03/17
- Re: [Qemu-devel] Re: branches are expensive, Paul Brook, 2009/03/17
- Re: [Qemu-devel] Re: branches are expensive, Avi Kivity, 2009/03/17
- [Qemu-devel] Re: branches are expensive, Steffen Liebergeld, 2009/03/19
- Re: [Qemu-devel] Re: branches are expensive, Laurent Desnogues, 2009/03/19
- [Qemu-devel] Re: branches are expensive, Steffen Liebergeld, 2009/03/19
- Re: [Qemu-devel] Re: branches are expensive, Laurent Desnogues, 2009/03/19
- Re: [Qemu-devel] Re: branches are expensive, Avi Kivity, 2009/03/19
- Re: [Qemu-devel] Re: branches are expensive, Paul Brook, 2009/03/19
[Qemu-devel] Re: branches are expensive,
Steffen Liebergeld <=
Re: [Qemu-devel] branches are expensive, Laurent Desnogues, 2009/03/17