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[Xen-devel] About CPU Affinity

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] About CPU Affinity
From: Saori Fukuta <fukuta.saori@xxxxxxxxxxxxxx>
Date: Fri, 11 May 2007 20:46:38 +0900
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Hi all,

I would like to set CPU Affinity like:
    vcpu#0 ---> pcpu#0
    vcpu#1 ---> pcpu#1
When I start the domain by configuration file defined [vcpus=2] and
[cpus="0,1"], the state become as follows.
    vcpu#0 ---> pcpu#0 or pcpu#1
    vcpu#1 ---> pcpu#0 or pcpu#1
So, I have to execute 2 commands to achieve the state.
# xm vcpu-pin foo 0 0
# xm vcpu-pin foo 1 1
# xm vcpu-list foo
Name                              ID  VCPU   CPU State   Time(s) CPU Affinity
foo                                0     0     0   r--      39.1 0
foo                                0     1     1   -b-      45.2 1

And there is another problem. The state returns to the previous state
after rebooting the domain. I think the rebooting command should keep
the state.

If I am allocating each 64 CPU in each domain, it is terribly painful to set 
the state again whenever rebooting the domains.

In addition, when we use the configuration file defined as follows:
    vcpus=2 + cpus="0" for DomA 
    vcpus=2 + cpus="1-63" for DomB
the state is useful only for a first time.
The domains will have following state because the state will be reset by
rebooting. It is not a good result.

1) first state
     vcpu pcpu
DomA    0    0
        1    0
DomB    0 1-63
        1 1-63

2) allocate 1 pcpu to each vcpu of DomA and decrease 1 pcpu from DomB
     vcpu pcpu
DomA    0    0
        1    1
DomB    0 2-63
        1 2-63

3) if rebooting DomB
     vcpu pcpu
DomA    0    0
        1    1
DomB    0 1-63
        1 1-63

I think it is important to keep the state even if rebooting the domain,
don't you think?

Saori Fukuta

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