[LU-12988] improve mount time on huge ldiskfs filesystem

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0
• Labels: LTS12 scalability
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

during Lustre server startup few small files need to be updated (e.g. config backup).
at this point buddy/bitmap cache is empty but mballoc wants to find a big chunk of free space for group preallocation and reads bitmaps one by one.
sometimes this can take a very long time.
one possisble workaround is to disable preallocation during mount.
a long term plan is to limit scanning and prefetch bitmaps, but this needs more efforts and will be tracked separately (LU-12970)

Issue Links

• is related to: LU-14453 LDISKFS-fs error (device xxx) in ldiskfs_do_update_inode:4840: Journal has aborted
• is related to: LU-13290 Write performance regression in ldiskfs patches
• is related to: LU-12970 improve mballoc for huge filesystems
• is related to: LU-12103 Improve block allocation for large partitions

Comments

[Gerrit Updater]

Minh Diep ([e-mail]) uploaded a new patch: https://review.whamcloud.com/37540
Subject: LU-12988 ldiskfs: mballoc to prefetch groups
Project: fs/lustre-release
Branch: b2_12
Current Patch Set: 1
Commit: d5735e733c84c18b632e26f482bb2663d34f2851

[Gerrit Updater]

Minh Diep ([e-mail]) uploaded a new patch: https://review.whamcloud.com/37539
Subject: LU-12988 ldiskfs: skip non-loaded groups at cr=0/1
Project: fs/lustre-release
Branch: b2_12
Current Patch Set: 1
Commit: a3febe05e566ab9dc81312fa441e49cddbd20eec

[Peter Jones]

Landed for 2.14

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/36893/
Subject: LU-12988 ldiskfs: mballoc to prefetch groups
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 05f31782be20fc4c46082dba02c10bcea59539e3

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/36891/
Subject: LU-12988 ldiskfs: skip non-loaded groups at cr=0/1
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 6a7a700a1490dfde6b60c2fb36df92a052059866

[Alex Zhuravlev]

hmm, I did remounted few times.. newly-created filesystem shouldn't demontrate any degradation w/o the patches even as a perfect group would be found immediately?

[Artem Blagodarenko (Inactive)]

bzzz I hope I am wrong...

I also get such optimistic results with my "adjusting table" script, but then I had realized that only FIRST MOUNT is slow. I recreated the partition and when mount became slow again even with my optimizations. bzzz, could you check your performance improvement on the fresh-created filesystem?

 

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/37155/
Subject: LU-12988 osd: do not use preallocation during mount
Project: fs/lustre-release
Branch: b2_12
Current Patch Set:
Commit: 2331cd1fa178b348d8aa048abbb5160ac9353461

[Alex Zhuravlev]

Do you also have Artem's mballoc patch applied?

yes, AFAICS. and that didn't help, probably fillness wasn't high enough. I'll check tomorrow.

[Andreas Dilger]

Do you also have Artem's mballoc patch applied? If not, should that be reverted from master, or do you think it makes sense to keep, but with lower thresholds (eg. 15%, 10%, 5% or whatever)?

[Alex Zhuravlev]

both https://review.whamcloud.com/#/c/36891/ and https://review.whamcloud.com/#/c/36893/ were used and need refresh, working on this..