Mailing List Archive

# HG changeset patch
# User kaf24@firebug.cl.cam.ac.uk
# Node ID f4f2ff82e7977f2dcd4ed6312451d04113569c2b
# Parent e7d7287ab222d9abd01f84dda21fa444798694ef
[XEND] An empirical and more conservative memory-overhead estimate for PV and HVM guests.

This patch calculates the overhead needed for HVM domains. If HVM is
supported by the hardware, I add a little ballooning overhead to
paravirtualized VMs also, to avoid low-memory situations. (There are
various unchecked alloc_domheap_pages calls in shadow*.c that I am
trying to avoid tripping over for now...) The values in this patch work
fine on 32 bit; I may update them later based on feedback and/or testing
on 64 bit.

Signed-off-by: Charles Coffing <ccoffing@novell.com>
---
tools/python/xen/xend/image.py | 24 ++++++++++++++++--------
1 files changed, 16 insertions(+), 8 deletions(-)

diff -r e7d7287ab222 -r f4f2ff82e797 tools/python/xen/xend/image.py
--- a/tools/python/xen/xend/image.py Fri May 19 16:07:36 2006 +0100
+++ b/tools/python/xen/xend/image.py Fri May 19 16:08:51 2006 +0100
@@ -19,6 +19,7 @@

import os, string
import re
+import math

import xen.lowlevel.xc
from xen.xend import sxp
@@ -141,11 +142,13 @@ class ImageHandler:
% (self.ostype, self.vm.getDomid(), str(result)))


- def getDomainMemory(self, mem):
+ def getDomainMemory(self, mem_kb):
"""@return The memory required, in KiB, by the domain to store the
- given amount, also in KiB. This is normally just mem, but HVM domains
- have overheads to account for."""
- return mem
+ given amount, also in KiB. This is normally just mem, but if HVM is
+ supported, keep a little extra free."""
+ if 'hvm' in xc.xeninfo()['xen_caps']:
+ mem_kb += 4*1024;
+ return mem_kb

def buildDomain(self):
"""Build the domain. Define in subclass."""
@@ -377,15 +380,20 @@ class HVMImageHandler(ImageHandler):
os.waitpid(self.pid, 0)
self.pid = 0

- def getDomainMemory(self, mem):
+ def getDomainMemory(self, mem_kb):
"""@see ImageHandler.getDomainMemory"""
- page_kb = 4
- extra_pages = 0
if os.uname()[4] == 'ia64':
page_kb = 16
# ROM size for guest firmware, ioreq page and xenstore page
extra_pages = 1024 + 2
- return mem + extra_pages * page_kb
+ else:
+ page_kb = 4
+ # This was derived emperically:
+ # 2.4 MB overhead per 1024 MB RAM + 8 MB constant
+ # + 4 to avoid low-memory condition
+ extra_mb = (2.4/1024) * (mem_kb/1024.0) + 12;
+ extra_pages = int( math.ceil( extra_mb*1024 / page_kb ))
+ return mem_kb + extra_pages * page_kb

def register_shutdown_watch(self):
""" add xen store watch on control/shutdown """

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