From: Heming Zhao <heming.zhao@suse.com>
To: Martin Wilck <mwilck@suse.de>,
LVM general discussion and development <linux-lvm@redhat.com>,
David Teigland <teigland@redhat.com>
Subject: Re: [linux-lvm] system boot time regression when using lvm2-2.03.05
Date: Fri, 6 Sep 2019 08:46:52 +0000 [thread overview]
Message-ID: <4552ae36-09fc-9145-d768-80b4ef572bca@suse.com> (raw)
In-Reply-To: <8b432efdabc3de82146ea6cb87b27c89556bf72e.camel@suse.de>
the _online_pvscan_one cost too much time when booting.
It mainly job is to create file in /run/lvm/pvs_online, which role is to replace lvmetad.
when comment out _online_pvscan_one, below folders are blank
/run/lvm/pvs_online & /run/lvm/vgs_online
I am not familiar with vg metadata layout. I GUESS the vg metadata is recorded on the first PV dev of PVs group devs. So the _online_pv_found job just use the vg metadata info to find/print whether or not this vg is ready. this part code cost time & less useful when system boot. Or in another word, this part code is not necessary for online vg/lv.
```c
_online_pv_found()
{
_online_pvid_file_create // call open() to create "/run/lvm/pvs_online/xx"
... ...
//zhm: below code just count the not online PV number.
dm_list_iterate_items(pvl, &vg->pvs) {
if (!_online_pvid_file_exists((const char *)&pvl->pv->id.uuid))
pvids_not_online++;
/* Check if one of the devs on the command line is in this VG. */
if (dev_args && dev_in_device_list(pvl->pv->dev, dev_args))
dev_args_in_vg = 1;
}
}
```
the core/key code for online lvs is _pvscan_aa():
_pvscan_aa
+-> _pvscan_aa_direct
| vgchange_activate
|
or
|
+-> process_each_vg //this func can work without reading /run/lvm/pvs_online/xx
_pvscan_aa_single
vgchange_activate
So my first patch partly backout commit 25b58310e3d6. To use process_each_vg active lvs, this func can work without reading /run/lvm/pvs_online/xx.
For the _pvscan_aa_direct(), I don't totally understand it. I need some time to dig it.
On 9/6/19 2:51 PM, Martin Wilck wrote:
> On Fri, 2019-09-06 at 05:01 +0000, Heming Zhao wrote:
>> I just tried to only apply below patch (didn't partly backout commit
>> 25b58310e3).
>> The attrs of lvs output still have 'a' bit.
>>
>> ```patch
>> +#if 0
>> if (!_online_pvscan_one(cmd, dev, NULL,
>> complete_vgnames, saved_vgs, 0, &pvid_without_metadata))
>> add_errors++;
>> +#endif
>
>
> IIUC this would mean that you skip David's "pvs_online" file generation
> entirely. How did the auto-activation happen, then?
>
>> ```
>>
>> the output of "systemd-analysis blame | head -n 10":
>> ```
>> 59.279s systemd-udev-settle.service
>> 39.979s dracut-initqueue.service
>> 1.676s lvm2-activation-net.service
>
> Could it be that lvm2-activation-net.service activated the VGs? I can
> imagine that that would be efficient, because when this service runs
> late in the boot process, I'd expect all PVs to be online, so
> everything can be activated in a single big swoop. Unfortunately, this
> wouldn't work in general, as it would be too late for booting from LVM
> volumes.
>
> However I thought all lvm2-acticvation... services were gone with LVM
> 2.03?
>
> Regards
> Martin
>
>
next prev parent reply other threads:[~2019-09-06 8:46 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 [this message]
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
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
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