[linux-lvm] lvmpolld causes high cpu load issue

[David Teigland]

On Wed, Aug 17, 2022 at 01:41:17PM +0000, Martin Wilck wrote:
> I like the general idea of the udev watch. It is the magic that causes
> newly created partitions to magically appear in the system, which is
> very convenient for users and wouldn't work otherwise. I can see that
> it might be inappropriate for LVM PVs. We can discuss changing the
> rules such that the watch is disabled for LVM devices (both PV and LV).
> I don't claim to overlook all possible side effects, but it might be
> worth a try. It would mean that newly created LVs, LV size changes etc.
> would not be visible in the system immediately. I suppose you could
> work around that in the LVM tools by triggering change events after
> operations like lvcreate.

I think it's worth looking into at least.  udev causes most of our major
problems, and causes things to fall apart everywhere at scale.


> Note: We were observing that watch events were triggered every 30s, for
> every PV, simultaneously.

Can you see what parts of the VG metadata are changing each time?  If it's
just metadata related to pvmove progress, then things are probably working
as designed, and we'd just be looking for optimizations (perhaps by some
code changes, or by reducing copies of metadata as suggested by Zdenek.)

Dave