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perf(computes): the host's info is read once per request

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The overview read the host's info four times, now once (12 libvirt calls).
A connection object keeps it next to the capabilities, and the VM page and
VM stats take it from there; the VM page's cached_reads block holds only
the VM's own data. Free memory is still read each time.
This commit is contained in:
catborise 2026-10-09 15:52:11 +03:00
parent 9adc808d26
commit 57f592df70
6 changed files with 57 additions and 32 deletions
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23
vrtManager/instance.py
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@ -490,13 +490,13 @@ class wvmInstance(wvmConnect):
@contextlib.contextmanager
def cached_reads(self):
"""
Within the block the domain XML (per flags value), the VM's state,
the host's info and each disk's volume are read from libvirt once
(the host's capabilities are read once per object anyway), for pages
that only read: a VM page reads the XML in some 30 getters and each
disk in two lists. 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.
Within the block the domain XML (per flags value), the VM's state and
each disk's volume are read from libvirt once (the host's info and
capabilities are read once per object anyway), for pages that only
read: a VM page reads the XML in some 30 getters and each disk in two
lists. 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")
@ -522,9 +522,6 @@ class wvmInstance(wvmConnect):
self._read_cache.clear()
return self.wvm.defineXML(xml)
def _host_info(self):
return self._cached("host info", self.wvm.getInfo)
def get_status(self):
"""
VIR_DOMAIN_NOSTATE = 0
@ -617,11 +614,11 @@ class wvmInstance(wvmConnect):
return description or ""
def get_max_memory(self):
return self._host_info()[1] * 1048576
return self.host_info[1] * 1048576
def get_max_cpus(self):
"""Get number of physical CPUs."""
hostinfo = self._host_info()
hostinfo = self.host_info
pcpus = hostinfo[4] * hostinfo[5] * hostinfo[6] * hostinfo[7]
return range(1, int(pcpus + 1))
@ -1308,7 +1305,7 @@ class wvmInstance(wvmConnect):
"nics": [{"dev": i, "rx": 0, "tx": 0} for i in range(len(nics))],
}
key = [self.instance.ID(), self._host_info()[2], disks, nics]
key = [self.instance.ID(), self.host_info[2], disks, nics]
unread = (-1,) * 8
def read():