Re: [lustre-discuss] Slow release of inodes on OST

[Andreas Dilger]

I haven't looked at that code recently, but I suspect that it is waiting for 
journal commits to complete
every 5s before sending another batch of destroys?  Is the filesystem otherwise 
idle or something?


On Feb 7, 2020, at 02:34, Åke Sandgren 
mailto:ake.sandg...@hpc2n.umu.se>> wrote:

Loocking at the osp.*.sync* values i see
osp.rsos-OST-osc-MDT.sync_changes=14174002
osp.rsos-OST-osc-MDT.sync_in_flight=0
osp.rsos-OST-osc-MDT.sync_in_progress=4096
osp.rsos-OST-osc-MDT.destroys_in_flight=14178098

And it takes 10 sec between changes of those values.

So is there any other tunable I can tweak on either OSS or MDS side?

On 2/6/20 6:58 AM, Andreas Dilger wrote:
On Feb 4, 2020, at 07:23, Åke Sandgren 
mailto:ake.sandg...@hpc2n.umu.se>
> wrote:

When I create a large number of files on an OST and then remove them,
the used inode count on the OST decreases very slowly, it takes several
hours for it to go from 3M to the correct ~10k.

(I'm running the io500 test suite)

Is there something I can do to make it release them faster?
Right now it has gone from 3M to 1.5M in 6 hours, (lfs df -i).

It this the object count or the file count?  Are you possibly using a lot of
stripes on the files being deleted that is multiplying the work needed?

These are SSD based OST's in case it matters.

The MDS controls the destroy of the OST objects, so there is a rate
limit, but ~700/s seems low to me, especially for SSD OSTs.

You could check "lctl get_param osp.*.sync*" on the MDS to see how
many destroys are pending.  Also, increasing osp.*.max_rpcs_in_flight
on the MDS might speed this up?  It should default to 32 per OST on
the MDS vs. default 8 for clients

Cheers, Andreas
--
Andreas Dilger
Principal Lustre Architect
Whamcloud







--
Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
Internet: a...@hpc2n.umu.se   Phone: +46 90 7866134 
Fax: +46 90-580 14
Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se
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Cheers, Andreas
--
Andreas Dilger
Principal Lustre Architect
Whamcloud






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Re: [lustre-discuss] Slow release of inodes on OST

[Åke Sandgren]

Loocking at the osp.*.sync* values i see
osp.rsos-OST-osc-MDT.sync_changes=14174002
osp.rsos-OST-osc-MDT.sync_in_flight=0
osp.rsos-OST-osc-MDT.sync_in_progress=4096
osp.rsos-OST-osc-MDT.destroys_in_flight=14178098

And it takes 10 sec between changes of those values.

So is there any other tunable I can tweak on either OSS or MDS side?

On 2/6/20 6:58 AM, Andreas Dilger wrote:
> On Feb 4, 2020, at 07:23, Åke Sandgren  > wrote:
>>
>> When I create a large number of files on an OST and then remove them,
>> the used inode count on the OST decreases very slowly, it takes several
>> hours for it to go from 3M to the correct ~10k.
>>
>> (I'm running the io500 test suite)
>>
>> Is there something I can do to make it release them faster?
>> Right now it has gone from 3M to 1.5M in 6 hours, (lfs df -i).
> 
> It this the object count or the file count?  Are you possibly using a lot of
> stripes on the files being deleted that is multiplying the work needed?
> 
>> These are SSD based OST's in case it matters.
> 
> The MDS controls the destroy of the OST objects, so there is a rate
> limit, but ~700/s seems low to me, especially for SSD OSTs.
> 
> You could check "lctl get_param osp.*.sync*" on the MDS to see how
> many destroys are pending.  Also, increasing osp.*.max_rpcs_in_flight
> on the MDS might speed this up?  It should default to 32 per OST on
> the MDS vs. default 8 for clients
> 
> Cheers, Andreas
> --
> Andreas Dilger
> Principal Lustre Architect
> Whamcloud
> 
> 
> 
> 
> 
> 

-- 
Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
Internet: a...@hpc2n.umu.se   Phone: +46 90 7866134 Fax: +46 90-580 14
Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se
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