From: David Teigland <teigland@redhat.com>
To: Peter Rajnoha <prajnoha@redhat.com>
Cc: zkabelac@redhat.com, bmarzins@redhat.com, martin.wilck@suse.com,
heming.zhao@suse.com, linux-lvm@redhat.com
Subject: Re: [linux-lvm] Discussion: performance issue on event activation mode
Date: Thu, 30 Sep 2021 10:55:42 -0500 [thread overview]
Message-ID: <20210930155542.GB32174@redhat.com> (raw)
In-Reply-To: <20210929213952.ws2qpmedaajs5wlx@alatyr-rpi.brq.redhat.com>
On Wed, Sep 29, 2021 at 11:39:52PM +0200, Peter Rajnoha wrote:
> Hmm, thinking about this, I've just realized one more important and related
> thing here I didn't realize before - the LVM regex filters! These may contain
> symlink names as one can find them in /dev. But for those symlinks, we need
> to be sure that the rules are already applied. This practically means that:
At least at RH we're enabling the devices file by default (meaning no
filter) in the same timeframe that we're looking at these activation
services. So, I don't think this is a big factor.
> - For non-event-based activation, we need udev-settle (so we're sure
> all the rules are applied for all devices we might be scanning).
>
> - For event-based activation, we need to be sure that we use "RUN"
> rule, not any of "IMPORT{program}" or "PROGRAM" rule. The difference
> is that the "RUN" rules are applied after all the other udev rules are
> already applied for current uevent, including creation of symlinks. And
> currently, we have IMPORT{program}="pvscan..." in our rule,
> unfortunately...
That's pretty subtle, I'm wary about propagating such specific and
delicate behavior, seems fragile.
> The nodes are already there, the symlinks could be missing because the
> udev rules haven't been processed yet.
>
> Non-event-based LVM activation needs to wait for settle for sure (because
> there's full scan across all devices).
>
> Event-based LVM activation just needs to be sure that:
>
> - the pvscan only scans the single device (the one for which there's
> the uevent currently being processed),
>
> - the pvscan should be called in a way that we have all the symlinks
> in place so the regex filter still works for symlinks (== putting
> the pvscan onto a RUN exec queue).
I think we're looking at a udev-settle dependency (or alternative) for all
cases, best to just make that explicit and consistent, and isolated in one
place. I'm not really seeing a downside to that. Then, focus efforts on
refining a replacement. If the subtle dependencies are spread around then
it's hard to extract and improve the unwanted parts.
Dave
_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
next prev parent reply other threads:[~2021-09-30 15:56 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
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 [this message]
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
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=20210930155542.GB32174@redhat.com \
--to=teigland@redhat.com \
--cc=bmarzins@redhat.com \
--cc=heming.zhao@suse.com \
--cc=linux-lvm@redhat.com \
--cc=martin.wilck@suse.com \
--cc=prajnoha@redhat.com \
--cc=zkabelac@redhat.com \
/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).