Not sure if it is a strace artifact, but in the slow case I see way more system
calls.
Those extra calls are what consumes the time.
It seems that after the call it does some cleanup.
But it does not a guided cleanup (e.g. closing all FDs it knows).
No - instead it seems to run a loop closing all FDs possible.
Now on Artful that runs 1-8192 (14bit), but on Zesty it is 1-1048575 (20 bit).
I think I remember having seen that close all FDs in the past, but can't
remember exactly where.
But while I miss that I remember the limits I see here.
libvirtd before Artful had LimitNOFILE=infinity in its service file.
On Artful and later it has LimitNOFILE=8192 (actually we had to raise that
recently for bigger installations, but never the less way smaller than 1M).
Adapting those limits makes it fast.
So summarizing what we know:
- some cleanup seems to clsoe all *possible* files
- the number of possible files got reduced in later libvirt version (for other
reasons)
- We can't SRU a smaller limit anyway, but looking forward I want to look into
the "close all" and which code does so.
- A solution for those affected is available by adapting LimitNOFILE in
/lib/systemd/system/libvirtd.service
I'll mark this as Won't Fix for the reasons outline in older releases,
but want to take a look if that "close all" can be optimized.
** Also affects: libvirt (Ubuntu Xenial)
Importance: Undecided
Status: New
** Also affects: libvirt (Ubuntu Zesty)
Importance: Undecided
Status: New
** Changed in: libvirt (Ubuntu Xenial)
Status: New => Won't Fix
** Changed in: libvirt (Ubuntu Zesty)
Status: New => Won't Fix
** Changed in: libvirt (Ubuntu)
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1727366
Title:
virsh start/destroy is too slow after adding firewall rule
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