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Re: [Qemu-devel] Re: branches are expensive
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] Re: branches are expensive |
Date: |
Tue, 17 Mar 2009 12:51:40 +0000 |
User-agent: |
KMail/1.9.9 |
> The ratio is quite bad. Do you have any documentation on when Qemu does the
> chaining and more important, when it does not. For example are
> unconditional jumps always chained, or only in one direction (forward or
> backward).
Direct jumps[1] within the same page are chained (including ). Indirect
jumps[2] and direct jumps to a different page are not chained. Chaining jumps
between pages would require breaking TB chains every time a TLB flush occurs.
Unchained jumps just a two stage lookup to cache frequently used entries.
Paul
[1] b, b<cc> and bl
[2] bx, mov pc, ldr pc, pop {pc}
- [Qemu-devel] branches are expensive, Steffen Liebergeld, 2009/03/17
- Re: [Qemu-devel] branches are expensive, Avi Kivity, 2009/03/17
- [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 <=
- 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, 2009/03/17
Re: [Qemu-devel] branches are expensive, Laurent Desnogues, 2009/03/17