From: David Teigland <teigland@redhat.com>
To: Martin Wilck <mwilck@suse.de>
Cc: LVM general discussion and development <linux-lvm@redhat.com>,
Heming Zhao <heming.zhao@suse.com>
Subject: Re: [linux-lvm] system boot time regression when using lvm2-2.03.05
Date: Tue, 10 Sep 2019 10:20:10 -0500 [thread overview]
Message-ID: <20190910152010.GA6789@redhat.com> (raw)
In-Reply-To: <b17fd5db54c852869c7ad8440f3492c367ced33d.camel@suse.de>
> > > _pvscan_aa
> > > vgchange_activate
> > > _activate_lvs_in_vg
> > > sync_local_dev_names
> > > fs_unlock
> > > dm_udev_wait <=== this point!
> > > ```
> Could you explain to us what's happening in this code? IIUC, an
> incoming uevent triggers pvscan, which then possibly triggers VG
> activation. That in turn would create more uevents. The pvscan process
> then waits for uevents for the tree "root" of the activated LVs to be
> processed.
>
> Can't we move this waiting logic out of the uevent handling? It seems
> weird to me that a process that acts on a uevent waits for the
> completion of another, later uevent. This is almost guaranteed to cause
> delays during "uevent storms". Is it really necessary?
>
> Maybe we could create a separate service that would be responsible for
> waiting for all these outstanding udev cookies?
Peter Rajnoha walked me through the details of this, and explained that a
timeout as you describe looks quite possible given default timeouts, and
that lvm doesn't really require that udev wait.
So, I pushed out this patch to allow pvscan with --noudevsync:
https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=3e5e7fd6c93517278b2451a08f47e16d052babbb
You'll want to add that option to lvm2-pvscan.service; we can hopefully
update the service to use that if things look good from testing.
next prev parent reply other threads:[~2019-09-10 15:20 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 13:52 [linux-lvm] system boot time regression when using lvm2-2.03.05 Heming Zhao
2019-08-29 14:37 ` David Teigland
2019-09-03 5:02 ` Heming Zhao
2019-09-03 15:17 ` David Teigland
2019-09-04 8:13 ` Heming Zhao
2019-09-05 12:35 ` Heming Zhao
2019-09-05 16:55 ` David Teigland
2019-09-06 4:31 ` Heming Zhao
2019-09-06 5:01 ` Heming Zhao
2019-09-06 6:51 ` Martin Wilck
2019-09-06 8:46 ` Heming Zhao
2019-09-06 14:15 ` David Teigland
2019-09-06 14:26 ` David Teigland
2019-09-06 14:03 ` David Teigland
2019-09-09 11:42 ` Heming Zhao
2019-09-09 14:09 ` David Teigland
2019-09-10 8:01 ` Martin Wilck
2019-09-10 15:20 ` David Teigland [this message]
2019-09-10 20:38 ` Zdenek Kabelac
2019-09-11 7:17 ` Martin Wilck
2019-09-11 9:13 ` Zdenek Kabelac
2019-09-12 13:58 ` Martin Wilck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190910152010.GA6789@redhat.com \
--to=teigland@redhat.com \
--cc=heming.zhao@suse.com \
--cc=linux-lvm@redhat.com \
--cc=mwilck@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).