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Re: [Qemu-devel] using mmap?
From: |
Mark Williamson |
Subject: |
Re: [Qemu-devel] using mmap? |
Date: |
Fri, 15 Dec 2006 16:32:06 +0000 |
User-agent: |
KMail/1.9.5 |
> I'm also doubtful how much benefit it gave in practice. I'm sure it would
> be good for synthetic CPU benchmarks. However using mmap significantly
> increases the overhead of context switches/tlb misses.
>
> To get good overall performance I suspect you're going to need closer
> cooperation with the kernel than mmap gives you. If you really want to make
> cross-emulation go fast I suggest working with the xen and/or kvm people to
> integrate qemu dynamic translation into those products. In theory I'd guess
> you should be able to plug it in as an alternative to the HVM code. I've no
> idea how close that is to being practical.
http://wiki.xensource.com/xenwiki/HVM/V2E
The v2e stuff allows execution state to be extracted from the real CPU,
plugged into QEmu for a bit for emulation, then transferred back to the real
CPU again. This is initially to be used for supporting Big Real Mode
emulation on HVM platforms. Later on it's planned to be used to accelerate
IO emulation further.
Eventually this may provide a means to use QEmu's translator to execute kernel
code whilst running user mode code under Xen. It may be that this isn't as
fast as other approaches, but it'd be a useful feature for Xen to have IMO.
Cheers,
Mark
> > Wouldn't this be a *significant*
> > performance enhancement for this setup which I'm sure is a common one?
> > Maybe this can be implemented for regular processes on the guest and
> > only use the softmmu for the kernel? Would someone point me in the
> > right direction for technical information? I have had to switch to
> > vmware free player until Qemu+KQEMU reaches a point of similar
> > performance, but I would really rather see Qemu advance further.
>
> If you're using an accelerator (eg. kqemu or kvm) this is all irelevant as
> most code isn't run by qemu, it's virtualized by the accelerator. qemu just
> does the IO emulation.
>
> Paul
>
>
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> Qemu-devel mailing list
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> http://lists.nongnu.org/mailman/listinfo/qemu-devel
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
- Re: [Qemu-devel] Qemu speed vs vmplayer?, (continued)
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Paul Brook, 2006/12/15
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Christian MICHON, 2006/12/15
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Lonnie Mendez, 2006/12/15
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Paul Brook, 2006/12/15
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Christian MICHON, 2006/12/15
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Paul Brook, 2006/12/15
- Message not available
- Message not available
- Message not available
- Re: [Qemu-devel] Qemu speed vs vmplayer?, it, 2006/12/17
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Lonnie Mendez, 2006/12/17
- Re: [Qemu-devel] Qemu speed w/ USB tablet emulation, Joseph Miller, 2006/12/19
- Re: [Qemu-devel] Qemu speed vs vmplayer?, Jamie Lokier, 2006/12/16
- Re: [Qemu-devel] using mmap?,
Mark Williamson <=
Re: [Qemu-devel] About performance of qemu-system-arm, Martin Guy, 2006/12/13