core-admin/qubes/qmemman/__init__.py

# pylint: skip-file

#
# The Qubes OS Project, http://www.qubes-os.org
#
# Copyright (C) 2010  Rafal Wojtczuk  <rafal@invisiblethingslab.com>
# Copyright (C) 2013  Marek Marczykowski <marmarek@invisiblethingslab.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, see <https://www.gnu.org/licenses/>.
#

import logging
import os
import string
import time

import functools
import xen.lowlevel.xc
import xen.lowlevel.xs

import qubes.qmemman.algo


no_progress_msg="VM refused to give back requested memory"
slow_memset_react_msg="VM didn't give back all requested memory"

class DomainState:
    def __init__(self, id):
        self.memory_current = 0     # the current memory size
        self.memory_actual = None   # the current memory allocation (what VM
                                    # is using or can use at any time)
        self.memory_maximum = None  # the maximum memory size
        self.mem_used = None		# used memory, computed based on meminfo
        self.id = id			    # domain id
        self.last_target = 0		# the last memset target
        self.no_progress = False    # no react to memset
        self.slow_memset_react = False  # slow react to memset (after few
                                        # tries still above target)

    def __repr__(self):
        return self.__dict__.__repr__()

class SystemState(object):
    def __init__(self):
        self.log = logging.getLogger('qmemman.systemstate')
        self.log.debug('SystemState()')

        self.domdict = {}
        self.xc = None
        self.xs = None

    def init(self):
        self.xc = xen.lowlevel.xc.xc()
        self.xs = xen.lowlevel.xs.xs()
        self.BALOON_DELAY = 0.1
        self.XEN_FREE_MEM_LEFT = 50*1024*1024
        self.XEN_FREE_MEM_MIN = 25*1024*1024
        # Overhead of per-page Xen structures, taken from OpenStack
        # nova/virt/xenapi/driver.py
        # see https://wiki.openstack.org/wiki/XenServer/Overhead
        # we divide total and free physical memory by this to get
        # "assignable" memory
        self.MEM_OVERHEAD_FACTOR = 1.0 / 1.00781
        try:
            self.ALL_PHYS_MEM = int(self.xc.physinfo()['total_memory']*1024 * self.MEM_OVERHEAD_FACTOR)
        except xen.lowlevel.xc.Error:
            self.ALL_PHYS_MEM = 0

    def add_domain(self, id):
        self.log.debug('add_domain(id={!r})'.format(id))
        self.domdict[id] = DomainState(id)
        # TODO: move to DomainState.__init__
        target_str = self.xs.read('', '/local/domain/' + id + '/memory/target')
        if target_str:
            self.domdict[id].last_target = int(target_str) * 1024

    def del_domain(self, id):
        self.log.debug('del_domain(id={!r})'.format(id))
        self.domdict.pop(id)

    def get_free_xen_memory(self):
        xen_free = int(self.xc.physinfo()['free_memory']*1024 *
                       self.MEM_OVERHEAD_FACTOR)
        # now check for domains which have assigned more memory than really
        # used - do not count it as "free", because domain is free to use it
        # at any time
        # assumption: self.refresh_memactual was called before
        # (so domdict[id].memory_actual is up to date)
        assigned_but_unused = functools.reduce(
            lambda acc, dom: acc + max(0, dom.last_target-dom.memory_current),
            self.domdict.values(),
            0
        )
        # If, at any time, Xen have less memory than XEN_FREE_MEM_MIN,
        # it is a failure of qmemman. Collect as much data as possible to
        # debug it
        if xen_free < self.XEN_FREE_MEM_MIN:
            self.log.error("Xen free = {!r} below acceptable value! "
                           "assigned_but_unused={!r}, domdict={!r}".format(
                xen_free, assigned_but_unused, self.domdict))
        elif xen_free < assigned_but_unused+self.XEN_FREE_MEM_MIN:
            self.log.error("Xen free = {!r} too small for satisfy assignments! "
                           "assigned_but_unused={!r}, domdict={!r}".format(
                xen_free, assigned_but_unused, self.domdict))
        return xen_free - assigned_but_unused

    # refresh information on memory assigned to all domains
    def refresh_memactual(self):
        for domain in self.xc.domain_getinfo():
            id = str(domain['domid'])
            if id in self.domdict:
                # real memory usage
                self.domdict[id].memory_current = domain['mem_kb']*1024
                # what VM is using or can use
                self.domdict[id].memory_actual = max(
                    self.domdict[id].memory_current,
                    self.domdict[id].last_target
                )
                self.domdict[id].memory_maximum = self.xs.read('', '/local/domain/%s/memory/static-max' % str(id))
                if self.domdict[id].memory_maximum:
                    self.domdict[id].memory_maximum = int(self.domdict[id].memory_maximum)*1024
                else:
                    self.domdict[id].memory_maximum = self.ALL_PHYS_MEM
                    # the previous line used to be
                    #   self.domdict[id].memory_maximum = domain[
                    #       'maxmem_kb']*1024
                    # but domain['maxmem_kb'] changes in self.mem_set as well,
                    # and this results in the memory never increasing
                    # in fact, the only possible case of nonexisting
                    # memory/static-max is dom0
                    # see #307

    def clear_outdated_error_markers(self):
        # Clear outdated errors
        for i in self.domdict.keys():
            if self.domdict[i].mem_used is None:
                continue
            # clear markers excluding VM from memory balance, if:
            #  - VM have responded to previous request (with some safety margin)
            #  - VM request more memory than it has assigned
            # The second condition avoids starving a VM, even when there is
            # some free memory available
            if self.domdict[i].memory_actual <= \
                    self.domdict[i].last_target + self.XEN_FREE_MEM_LEFT/2 or \
                    self.domdict[i].memory_actual < \
                    qubes.qmemman.algo.prefmem(self.domdict[i]):
                self.domdict[i].slow_memset_react = False
                self.domdict[i].no_progress = False

    # the below works (and is fast), but then 'xm list' shows unchanged
    # memory value
    def mem_set(self, id, val):
        self.log.info('mem-set domain {} to {}'.format(id, val))
        self.domdict[id].last_target = val
        # can happen in the middle of domain shutdown
        # apparently xc.lowlevel throws exceptions too
        try:
            self.xc.domain_setmaxmem(int(id), int(val/1024) + 1024) # LIBXL_MAXMEM_CONSTANT=1024
            self.xc.domain_set_target_mem(int(id), int(val / 1024))
        except:
            pass
        # VM sees about 16MB memory less, so adjust for it here - qmemman
        #  handle Xen view of memory
        self.xs.write('', '/local/domain/' + id + '/memory/target',
            str(int(val/1024 - 16 * 1024)))

    # this is called at the end of ballooning, when we have Xen free mem already
    # make sure that past mem_set will not decrease Xen free mem
    def inhibit_balloon_up(self):
        self.log.debug('inhibit_balloon_up()')
        for i in self.domdict.keys():
            dom = self.domdict[i]
            if dom.memory_actual is not None and dom.memory_actual + 200*1024 < dom.last_target:
                self.log.info(
                    'Preventing balloon up to {}'.format(dom.last_target))
                self.mem_set(i, dom.memory_actual)

    # perform memory ballooning, across all domains, to add "memsize" to Xen
    #  free memory
    def do_balloon(self, memsize):
        self.log.info('do_balloon(memsize={!r})'.format(memsize))
        CHECK_PERIOD_S = 3
        CHECK_MB_S = 100

        niter = 0
        prev_memory_actual = None

        for i in self.domdict.keys():
            self.domdict[i].no_progress = False

        #: number of loop iterations for CHECK_PERIOD_S seconds
        check_period = max(1, int((CHECK_PERIOD_S + 0.0) / self.BALOON_DELAY))
        #: number of free memory bytes expected to get during CHECK_PERIOD_S
        #: seconds
        check_delta = CHECK_PERIOD_S * CHECK_MB_S * 1024 * 1024
        #: helper array for holding free memory size, CHECK_PERIOD_S seconds
        #: ago, at every loop iteration
        xenfree_ring = [0] * check_period

        while True:
            self.log.debug('niter={:2d}'.format(niter))
            self.refresh_memactual()
            xenfree = self.get_free_xen_memory()
            self.log.info('xenfree={!r}'.format(xenfree))
            if xenfree >= memsize + self.XEN_FREE_MEM_MIN:
                self.inhibit_balloon_up()
                return True
            # fail the request if over past CHECK_PERIOD_S seconds,
            # we got less than CHECK_MB_S MB/s on average
            ring_slot = niter % check_period
            if niter >= check_period and xenfree < xenfree_ring[ring_slot] + check_delta:
                return False
            xenfree_ring[ring_slot] = xenfree
            if prev_memory_actual is not None:
                for i in prev_memory_actual.keys():
                    if prev_memory_actual[i] == self.domdict[i].memory_actual:
                        # domain not responding to memset requests, remove it
                        #  from donors
                        self.domdict[i].no_progress = True
                        self.log.info('domain {} stuck at {}'.format(i, self.domdict[i].memory_actual))
            memset_reqs = qubes.qmemman.algo.balloon(memsize + self.XEN_FREE_MEM_LEFT - xenfree, self.domdict)
            self.log.info('memset_reqs={!r}'.format(memset_reqs))
            if len(memset_reqs) == 0:
                return False
            prev_memory_actual = {}
            for i in memset_reqs:
                dom, mem = i
                self.mem_set(dom, mem)
                prev_memory_actual[dom] = self.domdict[dom].memory_actual
            self.log.debug('sleeping for {} s'.format(self.BALOON_DELAY))
            time.sleep(self.BALOON_DELAY)
            niter = niter + 1

    def refresh_meminfo(self, domid, untrusted_meminfo_key):
        self.log.debug(
            'refresh_meminfo(domid={}, untrusted_meminfo_key={!r})'.format(
                domid, untrusted_meminfo_key))

        qubes.qmemman.algo.refresh_meminfo_for_domain(
            self.domdict[domid], untrusted_meminfo_key)
        self.do_balance()

    # is the computed balance request big enough ?
    # so that we do not trash with small adjustments
    def is_balance_req_significant(self, memset_reqs, xenfree):
        self.log.debug(
            'is_balance_req_significant(memset_reqs={}, xenfree={})'.format(
                memset_reqs, xenfree))

        total_memory_transfer = 0
        MIN_TOTAL_MEMORY_TRANSFER = 150*1024*1024
        MIN_MEM_CHANGE_WHEN_UNDER_PREF = 15*1024*1024

        # If xenfree to low, return immediately
        if self.XEN_FREE_MEM_LEFT - xenfree > MIN_MEM_CHANGE_WHEN_UNDER_PREF:
            self.log.debug('xenfree is too low, returning')
            return True

        for rq in memset_reqs:
            dom, mem = rq
            last_target = self.domdict[dom].last_target
            memory_change = mem - last_target
            total_memory_transfer += abs(memory_change)
            pref = qubes.qmemman.algo.prefmem(self.domdict[dom])

            if 0 < last_target < pref and \
                    memory_change > MIN_MEM_CHANGE_WHEN_UNDER_PREF:
                self.log.info(
                    'dom {} is below pref, allowing balance'.format(dom))
                return True

        ret = total_memory_transfer + abs(xenfree - self.XEN_FREE_MEM_LEFT) > MIN_TOTAL_MEMORY_TRANSFER
        self.log.debug('is_balance_req_significant return {}'.format(ret))
        return ret


    def print_stats(self, xenfree, memset_reqs):
        for i in self.domdict.keys():
            if self.domdict[i].mem_used is not None:
                self.log.info('stat: dom {!r} act={} pref={} last_target={}'
                    '{}{}'.format(i,
                        self.domdict[i].memory_actual,
                        qubes.qmemman.algo.prefmem(self.domdict[i]),
                        self.domdict[i].last_target,
                        ' no_progress' if self.domdict[i].no_progress else '',
                        ' slow_memset_react'
                            if self.domdict[i].slow_memset_react else ''))

        self.log.info('stat: xenfree={} memset_reqs={}'.format(xenfree, memset_reqs))


    def do_balance(self):
        self.log.debug('do_balance()')
        if os.path.isfile('/var/run/qubes/do-not-membalance'):
            self.log.debug('do-not-membalance file preset, returning')
            return

        self.refresh_memactual()
        self.clear_outdated_error_markers()
        xenfree = self.get_free_xen_memory()
        memset_reqs = qubes.qmemman.algo.balance(xenfree - self.XEN_FREE_MEM_LEFT, self.domdict)
        if not self.is_balance_req_significant(memset_reqs, xenfree):
            return

        self.print_stats(xenfree, memset_reqs)

        prev_memactual = {}
        for i in self.domdict.keys():
            prev_memactual[i] = self.domdict[i].memory_actual
        for rq in memset_reqs:
            dom, mem = rq
            # Force to always have at least 0.9*self.XEN_FREE_MEM_LEFT (some
            # margin for rounding errors). Before giving memory to
            # domain, ensure that others have gave it back.
            # If not - wait a little.
            ntries = 5
            while self.get_free_xen_memory() - (mem - self.domdict[dom].memory_actual) < 0.9*self.XEN_FREE_MEM_LEFT:
                self.log.debug('do_balance dom={!r} sleeping ntries={}'.format(
                    dom, ntries))
                time.sleep(self.BALOON_DELAY)
                self.refresh_memactual()
                ntries -= 1
                if ntries <= 0:
                    # Waiting haven't helped; Find which domain get stuck and
                    # abort balance (after distributing what we have)
                    for rq2 in memset_reqs:
                        dom2, mem2 = rq2
                        if dom2 == dom:
                            # All donors have been processed
                            break
                        # allow some small margin
                        if self.domdict[dom2].memory_actual > self.domdict[dom2].last_target + self.XEN_FREE_MEM_LEFT/4:
                            # VM didn't react to memory request at all,
                            # remove from donors
                            if prev_memactual[dom2] == self.domdict[dom2].memory_actual:
                                self.log.warning(
                                    'dom {!r} didnt react to memory request'
                                    ' (holds {}, requested balloon down to {})'
                                        .format(dom2,
                                            self.domdict[dom2].memory_actual,
                                            mem2))
                                self.domdict[dom2].no_progress = True
                            else:
                                self.log.warning('dom {!r} still hold more'
                                    ' memory than have assigned ({} > {})'
                                        .format(dom2,
                                            self.domdict[dom2].memory_actual,
                                            mem2))
                                self.domdict[dom2].slow_memset_react = True
                    self.mem_set(dom, self.get_free_xen_memory() + self.domdict[dom].memory_actual - self.XEN_FREE_MEM_LEFT)
                    return

            self.mem_set(dom, mem)

#        for i in self.domdict.keys():
#            print 'domain ', i, ' meminfo=', self.domdict[i].mem_used, 'actual mem', self.domdict[i].memory_actual
#            print 'domain ', i, 'actual mem', self.domdict[i].memory_actual
#        print 'xen free mem', self.get_free_xen_memory()