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#===========================================================================
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#============================================================================
# Copyright (C) 2004, 2005 Mike Wray <mike.wray@hp.com>
# Copyright (C) 2005 XenSource Ltd
#============================================================================
import time
import xen.lowlevel.xc
import XendDomain
import XendRoot
from XendLogging import log
from XendError import VmError
PROC_XEN_BALLOON = '/proc/xen/balloon'
RETRY_LIMIT = 20
RETRY_LIMIT_INCR = 5
##
# The time to sleep between retries grows linearly, using this value (in
# seconds). When the system is lightly loaded, memory should be scrubbed and
# returned to the system very quickly, whereas when it is loaded, the system
# needs idle time to get the scrubbing done. This linear growth accommodates
# such requirements.
SLEEP_TIME_GROWTH = 0.1
# A mapping between easy-to-remember labels and the more verbose
# label actually shown in the PROC_XEN_BALLOON file.
labels = { 'current' : 'Current allocation',
'target' : 'Requested target',
'low-balloon' : 'Low-mem balloon',
'high-balloon' : 'High-mem balloon',
'limit' : 'Xen hard limit' }
def _get_proc_balloon(label):
"""Returns the value for the named label. Returns None if the label was
not found or the value was non-numeric."""
f = file(PROC_XEN_BALLOON, 'r')
try:
for line in f:
keyvalue = line.split(':')
if keyvalue[0] == label:
values = keyvalue[1].split()
if values[0].isdigit():
return int(values[0])
else:
return None
return None
finally:
f.close()
def get_dom0_current_alloc():
"""Returns the current memory allocation (in KiB) of dom0."""
kb = _get_proc_balloon(labels['current'])
if kb == None:
raise VmError('Failed to query current memory allocation of dom0.')
return kb
def get_dom0_target_alloc():
"""Returns the target memory allocation (in KiB) of dom0."""
kb = _get_proc_balloon(labels['target'])
if kb == None:
raise VmError('Failed to query target memory allocation of dom0.')
return kb
def free(need_mem):
"""Balloon out memory from the privileged domain so that there is the
specified required amount (in KiB) free.
"""
# We check whether there is enough free memory, and if not, instruct dom0
# to balloon out to free some up. Memory freed by a destroyed domain may
# not appear in the free_memory field immediately, because it needs to be
# scrubbed before it can be released to the free list, which is done
# asynchronously by Xen; ballooning is asynchronous also. Such memory
# does, however, need to be accounted for when calculating how much dom0
# needs to balloon. No matter where we expect the free memory to come
# from, we need to wait for it to become available.
#
# We are not allowed to balloon below dom0_min_mem, or if dom0_min_mem
# is 0, we cannot balloon at all. Memory can still become available
# through a rebooting domain, however.
#
# Eventually, we time out (presumably because there really isn't enough
# free memory).
#
# We don't want to set the memory target (triggering a watch) when that
# has already been done, but we do want to respond to changing memory
# usage, so we recheck the required alloc each time around the loop, but
# track the last used value so that we don't trigger too many watches.
xroot = XendRoot.instance()
xc = xen.lowlevel.xc.xc()
try:
dom0_min_mem = xroot.get_dom0_min_mem() * 1024
retries = 0
sleep_time = SLEEP_TIME_GROWTH
last_new_alloc = None
rlimit = RETRY_LIMIT
while retries < rlimit:
physinfo = xc.physinfo()
free_mem = physinfo['free_memory']
scrub_mem = physinfo['scrub_memory']
if free_mem >= need_mem:
log.debug("Balloon: %d KiB free; need %d; done.",
free_mem, need_mem)
return
if retries == 0:
rlimit += ((need_mem - free_mem)/1024/1024) * RETRY_LIMIT_INCR
log.debug("Balloon: %d KiB free; %d to scrub; need %d; retries: %d.",
free_mem, scrub_mem, need_mem, rlimit)
if dom0_min_mem > 0:
dom0_alloc = get_dom0_current_alloc()
new_alloc = dom0_alloc - (need_mem - free_mem - scrub_mem)
if free_mem + scrub_mem >= need_mem:
if last_new_alloc == None:
log.debug("Balloon: waiting on scrubbing")
last_new_alloc = dom0_alloc
else:
if (new_alloc >= dom0_min_mem and
new_alloc != last_new_alloc):
new_alloc_mb = new_alloc / 1024 # Round down
log.debug("Balloon: setting dom0 target to %d MiB.",
new_alloc_mb)
dom0 = XendDomain.instance().privilegedDomain()
dom0.setMemoryTarget(new_alloc_mb)
last_new_alloc = new_alloc
# Continue to retry, waiting for ballooning or scrubbing.
time.sleep(sleep_time)
if retries < 2 * RETRY_LIMIT:
sleep_time += SLEEP_TIME_GROWTH
retries += 1
# Not enough memory; diagnose the problem.
if dom0_min_mem == 0:
raise VmError(('Not enough free memory and dom0_min_mem is 0, so '
'I cannot release any more. I need %d KiB but '
'only have %d.') %
(need_mem, free_mem))
elif new_alloc < dom0_min_mem:
raise VmError(
('I need %d KiB, but dom0_min_mem is %d and shrinking to '
'%d KiB would leave only %d KiB free.') %
(need_mem, dom0_min_mem, dom0_min_mem,
free_mem + scrub_mem + dom0_alloc - dom0_min_mem))
else:
raise VmError('The privileged domain did not balloon!')
finally:
del xc
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