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Re: [Qemu-devel] Re: request : qemu-smp as target
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] Re: request : qemu-smp as target |
Date: |
Sat, 14 May 2005 12:31:21 +0100 |
User-agent: |
KMail/1.7.2 |
On Saturday 14 May 2005 10:37, Blue Swirl wrote:
> Hi,
>
> The architecture used in sparc target (sun4m) supports SMP up to a maximum
> of 16 CPUs. At hardware emulation level (hw/*, target-sparc/*), it would be
> easy to add the missing interprocessor interrupts, per-CPU counters and
> atomic instructions. It would also be simple to add the prom functions for
> starting/stopping CPUs to Proll. Maybe some days' work in total.
>
> Higher level (vl.c, cpu-exec.c) could need more work. Maybe Fabrice can
> enlighten us?
I guess you'd really want to simulate multiple CPUs with multiple host
threads. One of the additional problems could then be memory/cache coherency.
I'm not sure how much of a problem this would be in practice. If both host
and guest require the same (or no) explicit SMP memory barriert it's not a
problem. It the guest has stronger coherency requirements than the host we
have a problem.
> For some reason, Sparc performance is low (1/10 of native x86 nbench)
> compared to x86 (2/3). Simulating SMP on a uniprocessor would only decrease
> performance.
It think x86-on-x86 user-mode uses code-copying by default. ie. it runs a lot
of the the code unmodified. In my experience i386-softmmu is generally 10-15x
slower than native, and arm-user is 5-10x slower.
Paul
- [Qemu-devel] Re: request : qemu-smp as target, Blue Swirl, 2005/05/14
- Re: [Qemu-devel] Re: request : qemu-smp as target,
Paul Brook <=
- [Qemu-devel] Re: request : qemu-smp as target, Fabrice Bellard, 2005/05/14
- Re: [Qemu-devel] Re: request : qemu-smp as target, Jonas Maebe, 2005/05/14
- [Qemu-devel] Re: request : qemu-smp as target, Blue Swirl, 2005/05/14
- Re: [Qemu-devel] Re: request : qemu-smp as target, Joe Batt, 2005/05/14
- Re: [Qemu-devel] Re: request : qemu-smp as target, Paul Brook, 2005/05/17
- Re: [Qemu-devel] Re: request : qemu-smp as target, Joe Batt, 2005/05/17
- Re: [Qemu-devel] Re: request : qemu-smp as target, Paul Brook, 2005/05/17
- Re: [Qemu-devel] Re: request : qemu-smp as target, Mark Williamson, 2005/05/18
- Re[2]: [Qemu-devel] Re: request : qemu-smp as target, Igor Shmukler, 2005/05/18