On 07/29/2010 03:47 PM, Alexander Graf wrote:
On PPC we run PR=0 (kernel mode) code in PR=1 (user mode) and don't use the
hypervisor extensions.
While that is all great to show that virtualization is possible, there are
quite some cases where the emulation overhead of privileged instructions is
killing performance.
This patchset tackles exactly that issue. It introduces a paravirtual framework
using which KVM and Linux share a page to exchange register state with. That
way we don't have to switch to the hypervisor just to change a value of a
privileged register.
To prove my point, I ran the same test I did for the MMU optimizations against
the PV framework. Here are the results:
[without]
debian-powerpc:~# time for i in {1..1000}; do /bin/echo hello> /dev/null; done
real 0m14.659s
user 0m8.967s
sys 0m5.688s
[with]
debian-powerpc:~# time for i in {1..1000}; do /bin/echo hello> /dev/null; done
real 0m7.557s
user 0m4.121s
sys 0m3.426s
So this is a significant performance improvement! I'm quite happy how fast this
whole thing becomes :)
I tried to take all comments I've heard from people so far about such a PV
framework into account. In case you told me something before that is a no-go
and I still did it, please just tell me again.
To make use of this whole thing you also need patches to qemu and openbios. I
have them in my queue, but want to see this set upstream first before I start
sending patches to the other projects.
Now go and have fun with fast VMs on PPC! Get yourself a G5 on ebay and start
experiencing the power yourself. - heh
Applied this and your follow on 7-part series, thanks.
--
error compiling committee.c: too many arguments to function
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