j3d1/webvirtcloud
1
0
Fork 0
mirror of https://github.com/retspen/webvirtcloud synced 2026-11-09 03:36:48 +00:00
Code Issues Projects Releases Wiki Activity

perf(instances): the VM page reads each kind of domain XML once

Browse source 
The VM page's getters read the domain XML on their own: one load made
86 libvirt calls for a real VM, 29 of them for the same three XML
documents (live, live with secrets, persistent) and 6 for the host
capabilities. Each call is a round trip to the host.

wvmInstance.cached_reads() is a block in which _XMLDesc (per flags
value) and get_cap_xml are read from libvirt once; it ends with the
block, even on an error, does not nest, and _defineXML drops it.
Outside a block every read goes to libvirt as before. Only the VM page
view, which does not change the VM, uses it, around its rendering.
Views that change the VM keep reading fresh XML: most changes (devices,
QoS, memory) do not go through _defineXML, and several views read,
change and define more than once in one request.

Measured on the test host: 86 -> 55 calls (XMLDesc 29 -> 3,
getCapabilities 6 -> 1) for one VM, 82 -> 54 for another; the page took
0.23-0.25 s before, 0.14-0.15 s after. The HTML of both pages is
identical before and after (CSRF tokens aside). A test renders the page
on libvirt's test driver through the real getters: 25 XML reads before,
one per kind now.
This commit is contained in:
catborise 2026-10-05 21:24:07 +03:00
parent 2295673203
commit f5276655fd
4 changed files with 223 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

38
vrtManager/instance.py
View file

@ -186,6 +186,9 @@ class wvmInstances(wvmConnect):
class wvmInstance(wvmConnect):
# set by cached_reads(): libvirt answers reused within the block
_read_cache = None
def __init__(self, host, login, passwd, conn, vname, uuid=None):
wvmConnect.__init__(self, host, login, passwd, conn)
self._ip_cache = None
@ -249,12 +252,45 @@ class wvmInstance(wvmConnect):
def delete(self, flags=0):
self.instance.undefineFlags(flags)
@contextlib.contextmanager
def cached_reads(self):
"""
Within the block the domain XML (per flags value) and the host
capabilities are read from libvirt once, for pages that only read: a
VM page reads the XML in some 30 getters. Code that changes the VM
must not run inside: most changes (devices, QoS, memory) do not go
through _defineXML, the only call that drops the cache.
"""
if self._read_cache is not None:
raise RuntimeError("cached_reads blocks do not nest")
self._read_cache = {}
try:
yield self
finally:
self._read_cache = None
def _XMLDesc(self, flag):
return self.instance.XMLDesc(flag)
cache = self._read_cache
if cache is None:
return self.instance.XMLDesc(flag)
key = ("xml", flag)
if key not in cache:
cache[key] = self.instance.XMLDesc(flag)
return cache[key]
def _defineXML(self, xml):
if self._read_cache is not None:
self._read_cache.clear()
return self.wvm.defineXML(xml)
def get_cap_xml(self):
cache = self._read_cache
if cache is None:
return super().get_cap_xml()
if "capabilities" not in cache:
cache["capabilities"] = super().get_cap_xml()
return cache["capabilities"]
def get_status(self):
"""
VIR_DOMAIN_NOSTATE = 0