From: "heming.zhao@suse.com" <heming.zhao@suse.com>
To: David Teigland <teigland@redhat.com>,
Martin Wilck <martin.wilck@suse.com>
Cc: "linux-lvm@redhat.com" <linux-lvm@redhat.com>,
"zkabelac@redhat.com" <zkabelac@redhat.com>
Subject: Re: [linux-lvm] Discussion: performance issue on event activation mode
Date: Sat, 3 Jul 2021 19:49:21 +0800 [thread overview]
Message-ID: <50b3e710-a6b7-2cc5-04fc-63525f0d720c@suse.com> (raw)
In-Reply-To: <20210702220219.GB15057@redhat.com>
On 7/3/21 6:02 AM, David Teigland wrote:
> On Fri, Jul 02, 2021 at 09:22:03PM +0000, Martin Wilck wrote:
>> On Fr, 2021-07-02 at 16:09 -0500, David Teigland wrote:
>>> On Sun, Jun 06, 2021 at 02:15:23PM +0800, heming.zhao@suse.com wrote:
>>>> dev_cache_scan //order: O(n^2)
>>>> + _insert_dirs //O(n)
>>>> | if obtain_device_list_from_udev() true
>>>> | _insert_udev_dir //O(n)
>>>> |
>>>> + dev_cache_index_devs //O(n)
>>>
>>> I've been running some experiments and trying some patches to improve
>>> this. By setting obtain_device_list_from_udev=0, and using the
>>> attached
>>> patch to disable dev_cache_index_devs, the pvscan is much better.
>>>
>>> systemctl status lvm2-pvscan appears to show that the pvscan command
>>> itself runs for only 2-4 seconds, while the service as a whole takes
>>> around 15 seconds. See the 16 sec gap below from the end of pvscan
>>> to the systemd Started message. If that's accurate, the remaining
>>> delay
>>> would lie outside lvm.
>>>
>>> Jul 02 15:27:57 localhost.localdomain systemd[1]: Starting LVM event
>>> activation on device 253:1710...
>>> Jul 02 15:28:00 localhost.localdomain lvm[65620]: pvscan[65620] PV
>>> /dev/mapper/mpathalz online, VG 1ed02c7d-0019-43c4-91b5-f220f3521ba9
>>> is complete.
>>> Jul 02 15:28:00 localhost.localdomain lvm[65620]: pvscan[65620] VG
>>> 1ed02c7d-0019-43c4-91b5-f220f3521ba9 run autoactivation.
>>> Jul 02 15:28:00 localhost.localdomain lvm[65620]: 1 logical
>>> volume(s) in volume group "1ed02c7d-0019-43c4-91b5-f220f3521ba9" now
>>> active
>>
>> Printing this message is really the last thing that pvscan does?
>
> I've not seen anything measurable after that message. However, digging
> through the command init/exit paths I did find libudev setup/destroy calls
> that can also be skipped when the command is not accessing libudev info.
> A quick check seemed to show some further improvement from dropping those.
> (That will be part of the larger patch isolating libudev usage.)
>
> I'm still seeing significant delay between the apparent command exit and
> the systemd "Started" message, but this will require a little more work to
> prove.
>
I applied the patch and got the very similar result.
```with patch
# systemd-analyze blame
27.679s lvm2-pvscan@134:896.service
27.664s lvm2-pvscan@134:800.service
27.648s lvm2-pvscan@134:960.service
27.645s lvm2-pvscan@132:816.service
27.589s lvm2-pvscan@134:816.service
27.582s lvm2-pvscan@133:992.service
... ...
# systemctl status lvm2-pvscan@134:896.service
... ...
Jul 03 19:43:02 sle15sp2-base40g systemd[1]: Starting LVM event activation on device 134:896...
Jul 03 19:43:03 sle15sp2-base40g lvm[24817]: pvscan[24817] PV /dev/sdalm online, VG vg_sdalm is complet>
Jul 03 19:43:03 sle15sp2-base40g lvm[24817]: pvscan[24817] VG vg_sdalm run autoactivation.
Jul 03 19:43:03 sle15sp2-base40g lvm[24817]: 1 logical volume(s) in volume group "vg_sdalm" now active
Jul 03 19:43:30 sle15sp2-base40g systemd[1]: Started LVM event activation on device 134:896.
```
the 27.679s get from 19:43:30 minus 19:43:02.
and 27s is 10s quick than the lvm without patch (by today's test result)
```without patch
# systemd-analyze blame
37.650s lvm2-pvscan@133:992.service
37.650s lvm2-pvscan@133:1008.service
37.649s lvm2-pvscan@133:896.service
37.649s lvm2-pvscan@134:960.service
37.612s lvm2-pvscan@133:880.service
37.612s lvm2-pvscan@133:864.servic
... ...
# systemctl status lvm2-pvscan@133:992.service
... ...
Jul 03 19:31:28 sle15sp2-base40g systemd[1]: Starting LVM event activation on device 133:992...
Jul 03 19:31:30 sle15sp2-base40g lvm[24243]: pvscan[24243] PV /dev/sdalc online, VG vg_sdalc is complet>
Jul 03 19:31:30 sle15sp2-base40g lvm[24243]: pvscan[24243] VG vg_sdalc run autoactivation.
Jul 03 19:31:30 sle15sp2-base40g lvm[24243]: 1 logical volume(s) in volume group "vg_sdalc" now active
Jul 03 19:32:05 sle15sp2-base40g systemd[1]: Started LVM event activation on device 133:992.
```
I added log in lvm2 code, the time of log "1 logical volume(s) in volume
group "vg_sdalm" now active" is the real pvscan finished time. Martin
comment in previous mail is may right, systemd is may busy and delayed to
detect/see the pvscan service completion.
Thanks,
heming
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next prev parent reply other threads:[~2021-07-03 11:50 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
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 [this message]
2021-07-08 10:10 ` Tom Yan
2021-07-02 21:31 ` Tom Yan
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