Re: [linux-lvm] system boot time regression when using lvm2-2.03.05

[Heming Zhao <heming.zhao@suse.com>]

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
```

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
           1.605s initrd-switch-root.service
           1.330s NetworkManager-wait-online.service
           1.250s sssd.service
            958ms initrd-parse-etc.service
            931ms lvm2-activation-early.service
            701ms lvm2-pvscan@259:97.service
            700ms firewalld.service
```

On 9/6/19 12:31 PM, Heming Zhao wrote:
> The status:
> ```
> [root@f30-lvmroot ~]# systemd-analyze blame | less
> [root@f30-lvmroot ~]# pvs | tail -n 5
>     /dev/vdh95  vgtst-54           lvm2 a--   4.00m 4.00m
>     /dev/vdh96  vgtst-54           lvm2 a--   4.00m 4.00m
>     /dev/vdh97  vgtst-55           lvm2 a--   4.00m    0
>     /dev/vdh98  vgtst-55           lvm2 a--   4.00m 4.00m
>     /dev/vdh99  vgtst-55           lvm2 a--   4.00m 4.00m
> [root@f30-lvmroot ~]# vgs | tail -n 5
>     vgtst-56            16   1   0 wz--n- 64.00m 60.00m
>     vgtst-6             16   1   0 wz--n- 64.00m 60.00m
>     vgtst-7             16   1   0 wz--n- 64.00m 60.00m
>     vgtst-8             16   1   0 wz--n- 64.00m 60.00m
>     vgtst-9             16   1   0 wz--n- 64.00m 60.00m
> [root@f30-lvmroot ~]# lvs | tail -n 5
>     vgtst-56-lv56 vgtst-56           -wi-a-----    4.00m
>     vgtst-6-lv6   vgtst-6            -wi-a-----    4.00m
>     vgtst-7-lv7   vgtst-7            -wi-a-----    4.00m
>     vgtst-8-lv8   vgtst-8            -wi-a-----    4.00m
>     vgtst-9-lv9   vgtst-9            -wi-a-----    4.00m
> [root@f30-lvmroot ~]# pvs | wc -l
> 899
> [root@f30-lvmroot ~]# vgs | wc -l
> 58
> [root@f30-lvmroot ~]# lvs | wc -l
> 60
> [root@f30-lvmroot ~]# rpm -qa | grep lvm2
> lvm2-devel-2.03.06-3.fc30.x86_64
> lvm2-dbusd-2.03.06-3.fc30.noarch
> lvm2-2.03.06-3.fc30.x86_64
> lvm2-lockd-2.03.06-3.fc30.x86_64
> udisks2-lvm2-2.8.4-1.fc30.x86_64
> lvm2-libs-2.03.06-3.fc30.x86_64
> [root@f30-lvmroot ~]#
> ```
> 
> you can see the 'a' bit of lv attr.
> 
> 
> Yesterday I only showed the key change of the modification. below is the complete patch.
> 1>
> comment out calling _online_pvscan_one in pvscan_cache_cmd
> 2>
> partly backout (use "#if 0") your commit: 25b58310e3d606a85abc9bd50991ccb7ddcbfe25
> https://sourceware.org/git/?p=lvm2.git;a=commit;h=25b58310e3d606a85abc9bd50991ccb7ddcbfe25
> 
> ```patch
> diff --git a/tools/pvscan.c b/tools/pvscan.c
> index b025ae3e6b..52a50af962 100644
> --- a/tools/pvscan.c
> +++ b/tools/pvscan.c
> @@ -928,7 +928,7 @@ static int _online_vg_file_create(struct cmd_context *cmd, const char *vgname)
>     * We end up with a list of struct devices that we need to
>     * scan/read in order to process/activate the VG.
>     */
> -
> +#if 0
>    static int _get_devs_from_saved_vg(struct cmd_context *cmd, char *vgname,
>    				   struct dm_list *saved_vgs,
>    				   struct dm_list *devs)
> @@ -1126,6 +1126,7 @@ out:
>    	release_vg(vg);
>    	return ret;
>    }
> +#endif
>    
>    static int _pvscan_aa(struct cmd_context *cmd, struct pvscan_aa_params *pp,
>    		      struct dm_list *vgnames, struct dm_list *saved_vgs)
> @@ -1166,7 +1167,9 @@ static int _pvscan_aa(struct cmd_context *cmd, struct pvscan_aa_params *pp,
>    		destroy_processing_handle(cmd, handle);
>    		return ECMD_PROCESSED;
>    	}
> -
> +#if 1
> +	ret = process_each_vg(cmd, 0, NULL, NULL, vgnames, READ_FOR_ACTIVATE, 0, handle, _pvscan_aa_single);
> +#else
>    	if (dm_list_size(vgnames) == 1) {
>    		dm_list_iterate_items(sl, vgnames)
>    			ret = _pvscan_aa_direct(cmd, pp, (char *)sl->str, saved_vgs);
> @@ -1174,6 +1177,7 @@ static int _pvscan_aa(struct cmd_context *cmd, struct pvscan_aa_params *pp,
>    		/* FIXME: suppress label scan in process_each if label scan already done? */
>    		ret = process_each_vg(cmd, 0, NULL, NULL, vgnames, READ_FOR_ACTIVATE, 0, handle, _pvscan_aa_single);
>    	}
> +#endif
>    
>    	destroy_processing_handle(cmd, handle);
>    
> @@ -1418,9 +1422,10 @@ int pvscan_cache_cmd(struct cmd_context *cmd, int argc, char **argv)
>    			}
>    
>    			add_single_count++;
> -
> +#if 0
>    			if (!_online_pvscan_one(cmd, dev, NULL, complete_vgnames, saved_vgs, 0, &pvid_without_metadata))
>    				add_errors++;
> +#endif
>    		}
>    	}
> ```
> 
> 
> On 9/6/19 12:55 AM, David Teigland wrote:
>> On Thu, Sep 05, 2019 at 12:35:53PM +0000, Heming Zhao wrote:
>>> In pvscan_cache_cmd, the code in below area "#if 0 .. #endif take a huge
>>> time. When I used below modified code to boot, the time reduced from
>>> 1min to 1.389s.
>>
>> That stops the command from doing any work.  I suspect that in your tests,
>> the "fast" case is not doing any activation, and the "slow" case is.
>> Please check where the LVs are being activated in the fast case.
>>
>>
> 
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