[linux-lvm] Discussion: performance issue on event activation mode

David Teigland teigland at redhat.com
Mon Jun 7 21:48:35 UTC 2021

On Mon, Jun 07, 2021 at 03:48:30PM +0000, Martin Wilck wrote:
> On So, 2021-06-06 at 14:15 +0800, heming.zhao at suse.com wrote:
> > 
> > 1. During boot phase, lvm2 automatically swithes to direct activation
> > mode
> > ("event_activation = 0"). After booted, switch back to the event
> > activation mode.
> > 
> > Booting phase is a speical stage. *During boot*, we could "pretend"
> > that direct
> > activation (event_activation=0) is set, and rely on lvm2-activation-
> > *.service
> > for PV detection. Once lvm2-activation-net.service has finished, we
> > could
> > "switch on" event activation.
> I like this idea. Alternatively, we could discuss disabling event
> activation only in the "coldplug" phase after switching root (i.e.
> between start of systemd-udev-trigger.service and lvm2-
> activation.service), because that's the critical time span during which
> 1000s of events can happen simultaneously.

If there are say 1000 PVs already present on the system, there could be
real savings in having one lvm command process all 1000, and then switch
over to processing uevents for any further devices afterward.  The switch
over would be delicate because of the obvious races involved with new devs
appearing, but probably feasible.  I'd like to see the scale of
improvement from a proof of concept before we spend too much time on the


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