Add the ability to define VBD QoS policy in the xend layer.
Consider the following vbd entry:
vbd = [
'phy:/dev/server/virtualmachine1-disk,xvda1,w,credit=5000/s@50ms',
]
This means that a VM may perform 5000 I/O operations per second, with
credit being replenished every 50 milliseconds.
The 'credit' xenstore value is by the blkback driver to ratelimit I/O
operations for the specific device.
Signed-off-by: William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
---
README.sxpcfg | 1 +
xen/xend/server/blkif.py | 43 ++++++++++++++++++++++++++++++++++++++++---
2 files changed, 41 insertions(+), 3 deletions(-)
diff --git a/tools/python/README.sxpcfg b/tools/python/README.sxpcfg
--- a/tools/python/README.sxpcfg
+++ b/tools/python/README.sxpcfg
@@ -82,6 +82,7 @@
- uname
- dev (ioemu:, .. etc)
- mode (r, w. w!)
+ - credit
vif
- type
diff --git a/tools/python/xen/xend/server/blkif.py
b/tools/python/xen/xend/server/blkif.py
--- a/tools/python/xen/xend/server/blkif.py
+++ b/tools/python/xen/xend/server/blkif.py
@@ -42,6 +42,37 @@
return os.access(auxbin.scripts_dir() + '/block-%s' % protocol,
os.X_OK)
+ def _calculateRateLimit(self, credstr):
+ """Calculate the rate limit, given a string like: 5000/s@50ms.
+ If this fails, the limit is unlimited.
+ """
+ credit_per_interval = 0xffffffffL
+ interval_usecs = 0L
+
+ credit_re = re.compile("^([0-9]+)/s(@([0-9]+)([mu]?)s)?$")
+
+ m = credit_re.match(credstr)
+ if m:
+ credit_per_sec = m.group(1)
+
+ if m.group(2) is None:
+ interval_usecs = 50000L # 50ms default
+ else:
+ interval_usecs = long(m.group(5))
+ if m.group(3) == '':
+ interval_usecs *= 1000 * 1000
+ elif m.group(3) == 'm':
+ interval_usecs *= 1000
+
+ credit_per_interval = (credit_per_sec * interval_usecs) / 1000000L
+
+ # overflow / underflow checking: default to unlimited rate
+ if credit_per_interval == 0 or credit_per_interval > 0xffffffffL
or \
+ interval_usecs == 0 or interval_usecs > 0xffffffffL:
+ credit_per_interval = 0xffffffffL
+ interval_usecs = 0L
+
+ return "%lu,%lu" % (credit_per_interval, interval_usecs)
def getDeviceDetails(self, config):
"""@see DevController.getDeviceDetails"""
@@ -91,6 +122,10 @@
if security.on() == xsconstants.XS_POLICY_USE:
self.do_access_control(config, uname)
+ cred = config.get('credit', '')
+ if cred:
+ back['credit'] = self._calculateRateLimit(cred)
+
(device_path, devid) = blkif.blkdev_name_to_number(dev)
if devid is None:
raise VmError('Unable to find number for device (%s)' % (dev))
@@ -153,12 +188,12 @@
config = DevController.getDeviceConfiguration(self, devid, transaction)
if transaction is None:
devinfo = self.readBackend(devid, 'dev', 'type', 'params', 'mode',
- 'uuid', 'bootable')
+ 'uuid', 'bootable', 'credit')
else:
devinfo = self.readBackendTxn(transaction, devid,
'dev', 'type', 'params', 'mode',
'uuid',
- 'bootable')
- dev, typ, params, mode, uuid, bootable = devinfo
+ 'bootable', 'credit')
+ dev, typ, params, mode, uuid, bootable, credit = devinfo
if dev:
if transaction is None:
@@ -178,6 +213,8 @@
config['uuid'] = uuid
if bootable != None:
config['bootable'] = int(bootable)
+ if credit:
+ config['credit'] = credit
proto = self.readFrontend(devid, 'protocol')
if proto:
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