This gist pins unpinned vcpus for VMs running under xen. It assumes that dom0 vcpus are pinned via kernel command line (e.g. dom0_max_vcpus=1 dom0_vcpus_pin=true)

pin-vcpus.py

#!/usr/bin/env python

# Marcus Furlong <furlongm@vpac.org> 4/4/2012
# Pin vcpus on xen

import sys
sys.path.insert(1, '/usr/lib/xen-4.0/lib/python')
sys.path.insert(1, '/usr/lib/xen-4.0/lib/python/xen/xm')

import os
import sys
import xml.dom.minidom

import warnings
warnings.filterwarnings('ignore', category=FutureWarning)

from xen.xend import sxp
from xen.xend import XendClient

from xen.util.xmlrpcclient import ServerProxy
from xen.util import auxbin


from xen.xend import XendOptions
xoptions = XendOptions.instance()

import signal
signal.signal(signal.SIGINT, signal.SIG_DFL)

XM_CONFIG_FILE_ENVVAR = 'XM_CONFIG_FILE'
XM_CONFIG_FILE_DEFAULT = auxbin.xen_configdir() + '/xm-config.xml'

# Supported types of server
SERVER_LEGACY_XMLRPC = 'LegacyXMLRPC'
SERVER_XEN_API = 'Xen-API'


def pin_vcpus():
    doms = server.xend.domains_with_state(False, 'all', False)
    dominfo = map(server.xend.domain.getVCPUInfo, doms)

    nr_cpus = 0

    for x in server.xend.node.info()[1:]:
        if len(x) > 1 and x[0] == 'nr_cpus':
            nr_cpus = int(x[1])

    print "Host has %s physical CPUS" % nr_cpus

    nonpinned = []
    dom0_cpus = []
    pcpumap = {}

    dom0 = server.xend.domain.getVCPUInfo(0)
    for vcpu in sxp.children(dom0, 'vcpu'):
        cpumap = list(sxp.child_value(vcpu, 'cpumap'))
        for pcpu in cpumap:
            dom0_cpus.append(pcpu)

    for i in range(0, nr_cpus):
        if i in dom0_cpus:
            pcpumap[i] = [0]
        else:
            pcpumap[i] = []

    for dom in dominfo:

        def get_info(n):
            return sxp.child_value(dom, n)

        name = get_info('name')
        domid = get_info('domid')
        if domid is not None:
            domid = str(domid)
        else:
            domid = ''

        for vcpu in sxp.children(dom, 'vcpu'):

            def vinfo(n, t):
                return t(sxp.child_value(vcpu, n))

            number = vinfo('number', int)
            cpumap = vinfo('cpumap', list)

            print '%(name)-32s %(domid)5s %(number)5d %(cpumap)s' % locals()

            if domid != '0':
                for cpu in cpumap:
                    pcpumap[cpu].append(int(domid))

            if len(cpumap) > 1:
                nonpinned.append([domid, number])

    vcpus_to_pin = len(nonpinned)
    print "There are %s vCPUS to pin" % vcpus_to_pin
    print "Domain-0 is using CPUs %s" % dom0_cpus
    print "%s CPUS are available for pinning" % (nr_cpus - len(dom0_cpus))

    if vcpus_to_pin > 0:

        def get_minlevel(pcpumap, minlevel=50):
            for pcpu in pcpumap:
                if len(pcpumap[pcpu]) < minlevel and pcpu not in dom0_cpus:
                    minlevel = len(pcpumap[pcpu])
            return minlevel

        minlevel = get_minlevel(pcpumap)
        for dom_vcpu in nonpinned:
            for pcpu in pcpumap:
                if len(pcpumap[pcpu]) > minlevel or pcpu in dom0_cpus:
                    continue
                else:
                    domain_id = str(dom_vcpu[0])
                    vcpu_id = str(dom_vcpu[1])
                    cpu_id = str(pcpu)
                    pcpumap[pcpu].append(int(dom_vcpu[0]))
                    print >> sys.stderr, ("xm vcpu-pin %s %s %s" %
                                          (domain_id, vcpu_id, cpu_id))
                    xm_vcpu_pin([domain_id, vcpu_id, cpu_id])
                    minlevel = get_minlevel(pcpumap)
                    break

        print >> sys.stderr, ("%s vCPUs pinned" % vcpus_to_pin)
    else:
        print "No vCPUs need pinning."


def xm_vcpu_pin(args):

    def cpu_make_map(cpulist):
        cpus = []
        for c in cpulist.split(','):
            if c == '':
                continue
            if c.find('-') != -1:
                (x, y) = c.split('-')
                for i in range(int(x), int(y) + 1):
                    cpus.append(int(i))
            else:
                # remove this element from the list
                if c[0] == '^':
                    cpus = [x for x in cpus if x != int(c[1:])]
                else:
                    cpus.append(int(c))
        cpus.sort()
        return ",".join(map(str, cpus))

    dom = args[0]
    vcpu = args[1]
    cpumap = cpu_make_map(args[2])

    server.xend.domain.pincpu(dom, vcpu, cpumap)


def parseServer():
    if config:
        server = config.getElementsByTagName('server')
        if server:
            st = server[0].getAttribute('type')
            if st != SERVER_XEN_API and st != SERVER_LEGACY_XMLRPC:
                print >> sys.stderr, ('Invalid server type %s; using %s.' %
                                     (st, SERVER_LEGACY_XMLRPC))
                st = SERVER_LEGACY_XMLRPC
            return (st, server[0].getAttribute('uri'))

    return SERVER_LEGACY_XMLRPC, XendClient.uri


def parseAuthentication():
    server = config.getElementsByTagName('server')[0]
    return (server.getAttribute('username'),
            server.getAttribute('password'))

if __name__ == "__main__":
    print "WARNING: this program assumes that dom0_vcpus_pin=true has been"
    print "set on the kernel command line."
    xmConfigFile = os.getenv(XM_CONFIG_FILE_ENVVAR, XM_CONFIG_FILE_DEFAULT)
    config = None
    if os.path.isfile(xmConfigFile):
        try:
            config = xml.dom.minidom.parse(xmConfigFile)
        except:
            print >> sys.stderr, ('Ignoring invalid configuration file %s.' %
                                 xmConfigFile)
    serverType, serverURI = parseServer()
    server = ServerProxy(serverURI)
    pin_vcpus()