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From: Peter Rajnoha <prajnoha@redhat.com>
To: LVM general discussion and development <linux-lvm@redhat.com>
Cc: "zkabelac@redhat.com" <zkabelac@redhat.com>,
	Heming Zhao <heming.zhao@suse.com>,
	Martin Wilck <martin.wilck@suse.com>
Subject: Re: [linux-lvm] Discussion: performance issue on event activation mode
Date: Tue, 8 Jun 2021 14:29:01 +0200	[thread overview]
Message-ID: <20210608122901.o7nw3v56kt756acu@alatyr-rpi.brq.redhat.com> (raw)
In-Reply-To: <20210607214835.GB8181@redhat.com>

On Mon 07 Jun 2021 16:48, David Teigland wrote:
> On Mon, Jun 07, 2021 at 03:48:30PM +0000, Martin Wilck wrote:
> > On So, 2021-06-06 at 14:15 +0800, heming.zhao@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.

Maybe to avoid the race, we could possibly write the proposed
"/run/lvm2/boot-finished" right before we initiate scanning in "vgchange
-aay" that is a part of the lvm2-activation-net.service (the last
service to do the direct activation).

A few event-based pvscans could fire during the window between
"scan initiated phase" in lvm2-activation-net.service's "ExecStart=vgchange -aay..."
and the originally proposed "ExecStartPost=/bin/touch /run/lvm2/boot-finished",
but I think still better than missing important uevents completely in
this window.

Peter

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  reply	other threads:[~2021-06-08 12:29 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06  6:15 [linux-lvm] Discussion: performance issue on event activation mode heming.zhao
2021-06-06 16:35 ` Roger Heflin
2021-06-07 10:27   ` Martin Wilck
2021-06-07 15:30     ` heming.zhao
2021-06-07 15:45       ` Martin Wilck
2021-06-07 20:52       ` Roger Heflin
2021-06-07 21:30     ` David Teigland
2021-06-08  8:26       ` Martin Wilck
2021-06-08 15:39         ` David Teigland
2021-06-08 15:47           ` Martin Wilck
2021-06-08 16:02             ` Zdenek Kabelac
2021-06-08 16:05               ` Martin Wilck
2021-06-08 16:03             ` David Teigland
2021-06-08 16:07               ` Martin Wilck
2021-06-15 17:03           ` David Teigland
2021-06-15 18:21             ` Zdenek Kabelac
2021-06-16 16:18             ` heming.zhao
2021-06-16 16:38               ` David Teigland
2021-06-17  3:46                 ` heming.zhao
2021-06-17 15:27                   ` David Teigland
2021-06-08 16:49         ` heming.zhao
2021-06-08 16:18       ` heming.zhao
2021-06-09  4:01         ` heming.zhao
2021-06-09  5:37           ` Heming Zhao
2021-06-09 18:59             ` David Teigland
2021-06-10 17:23               ` heming.zhao
2021-06-07 15:48 ` Martin Wilck
2021-06-07 16:31   ` Zdenek Kabelac
2021-06-07 21:48   ` David Teigland
2021-06-08 12:29     ` Peter Rajnoha [this message]
2021-06-08 13:23       ` Martin Wilck
2021-06-08 13:41         ` Peter Rajnoha
2021-06-08 13:46           ` Zdenek Kabelac
2021-06-08 13:56             ` Peter Rajnoha
2021-06-08 14:23               ` Zdenek Kabelac
2021-06-08 14:48               ` Martin Wilck
2021-06-08 15:19                 ` Peter Rajnoha
2021-06-08 15:39                   ` Martin Wilck
2021-09-09 19:44         ` David Teigland
2021-09-10 17:38           ` Martin Wilck
2021-09-12 16:51             ` heming.zhao
2021-09-27 10:00           ` Peter Rajnoha
2021-09-27 15:38             ` David Teigland
2021-09-28  6:34               ` Martin Wilck
2021-09-28 14:42                 ` David Teigland
2021-09-28 15:16                   ` Martin Wilck
2021-09-28 15:31                     ` Martin Wilck
2021-09-28 15:56                     ` David Teigland
2021-09-28 18:03                       ` Benjamin Marzinski
2021-09-28 17:42                     ` Benjamin Marzinski
2021-09-28 19:15                       ` Martin Wilck
2021-09-29 22:06                       ` Peter Rajnoha
2021-09-30  7:51                         ` Martin Wilck
2021-09-30  8:07                           ` heming.zhao
2021-09-30  9:31                             ` Martin Wilck
2021-09-30 11:41                             ` Peter Rajnoha
2021-09-30 15:32                               ` heming.zhao
2021-10-01  7:41                                 ` Martin Wilck
2021-10-01  8:08                                   ` Peter Rajnoha
2021-09-30 11:29                           ` Peter Rajnoha
2021-09-30 16:04                             ` David Teigland
2021-09-30 14:41                           ` Benjamin Marzinski
2021-10-01  7:42                             ` Martin Wilck
2021-09-29 21:53                 ` Peter Rajnoha
2021-09-30  7:45                   ` Martin Wilck
2021-09-29 21:39               ` Peter Rajnoha
2021-09-30  7:22                 ` Martin Wilck
2021-09-30 14:26                   ` David Teigland
2021-09-30 15:55                 ` David Teigland
2021-10-01  8:00                   ` Peter Rajnoha
2021-10-18  6:24                   ` Martin Wilck
2021-10-18 15:04                     ` David Teigland
2021-10-18 16:56                       ` heming.zhao
2021-10-18 21:51                       ` Zdenek Kabelac
2021-10-19 17:18                         ` David Teigland
2021-10-20 14:40                       ` Martin Wilck
2021-10-20 14:50                         ` David Teigland
2021-10-20 14:54                           ` Martin Wilck
2021-10-20 15:12                             ` David Teigland
2021-06-07 16:40 ` David Teigland
2021-07-02 21:09 ` David Teigland
2021-07-02 21:22   ` Martin Wilck
2021-07-02 22:02     ` David Teigland
2021-07-03 11:49       ` heming.zhao
2021-07-08 10:10         ` Tom Yan
2021-07-02 21:31   ` Tom Yan

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