# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID cc303cdf88099ecdae5b1be53b3ef1cadee2df28
# Parent e0741ec5ec52d222c39324c672fc31742b2a9a88
The attached patch cleans up the parsing of /proc/xen/balloon that
occurs in xend. Currently, the parsing is hard-coded; it expects that
the desired number is on the first line. My patch is more robust; it
lets values be retrieved by a label. It also exposes a few functions to
retrieve the current allocation and the target allocation.
By abstracting this a little better, I'll be able to address a few
other issues in subsequent patches. Mostly, this allows for better
error checking and guidance for the user. For example, by exposing
get_dom0_current_alloc(), we can (elsewhere, in a later patch) calculate
how large of a VM could potentially be started. This is useful, as it
lets simple VM-creation GUIs guide the user towards reasonable memory
values for new VMs.
Signed-off-by: Charles Coffing <ccoffing@xxxxxxxxxx>
diff -r e0741ec5ec52 -r cc303cdf8809 tools/python/xen/xend/balloon.py
--- a/tools/python/xen/xend/balloon.py Fri Mar 10 09:54:25 2006
+++ b/tools/python/xen/xend/balloon.py Fri Mar 10 10:05:59 2006
@@ -27,7 +27,8 @@
from XendError import VmError
-PROC_XEN_BALLOON = "/proc/xen/balloon"
+PROC_XEN_BALLOON = '/proc/xen/balloon'
+
BALLOON_OUT_SLACK = 1 # MiB. We need this because the physinfo details are
# rounded.
RETRY_LIMIT = 10
@@ -39,6 +40,47 @@
# 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 MiB) of dom0."""
+
+ kb = _get_proc_balloon(labels['current'])
+ if kb == None:
+ raise VmError('Failed to query current memory allocation of dom0.')
+ return kb / 1024
+
+def get_dom0_target_alloc():
+ """Returns the target memory allocation (in MiB) of dom0."""
+
+ kb = _get_proc_balloon(labels['target'])
+ if kb == None:
+ raise VmError('Failed to query target memory allocation of dom0.')
+ return kb / 1024
def free(required):
"""Balloon out memory from the privileged domain so that there is the
@@ -88,7 +130,7 @@
log.debug("Balloon: free %d; need %d.", free_mem, need_mem)
if dom0_min_mem > 0:
- dom0_alloc = _get_dom0_alloc()
+ dom0_alloc = get_dom0_current_alloc()
new_alloc = dom0_alloc - (need_mem - free_mem)
if (new_alloc >= dom0_min_mem and
@@ -121,20 +163,3 @@
finally:
del xc
-
-
-def _get_dom0_alloc():
- """Return current allocation memory of dom0 (in MiB). Return 0 on error"""
-
- f = file(PROC_XEN_BALLOON, 'r')
- try:
- line = f.readline()
- for x in line.split():
- for n in x:
- if not n.isdigit():
- break
- else:
- return int(x) / 1024
- return 0
- finally:
- f.close()
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