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
>
>
_______________________________________________
linux-lvm mailing list
linux-lvm@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
