doc/cephfs: document purge queue and its perf counters by dparmar18 · Pull Request #60794 · ceph/ceph

dparmar18 · 2024-11-21T22:11:55Z

Fixes: https://tracker.ceph.com/issues/68571

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dparmar18 · 2024-11-25T13:30:39Z

Request @ceph/cephfs for suggestions/corrections.

doc/cephfs/purge-queue.rst

zdover23 · 2024-12-20T00:16:03Z

jenkins test docs

zdover23 · 2024-12-20T00:25:07Z

@dparmar18, I'll take care of all the corrections and alterations. Thanks for this contribution!

anthonyeleven · 2024-12-20T01:51:21Z

doc/cephfs/purge-queue.rst

+
+MDS maintains a data structure known as **Purge Queue** which is responsible
+for managing and executing the sequential deletion of files.
+There is a Purge queue for every MDS rank. Purge queues consist of purge items


The first Purge here should be lowercased.

There's a lot of stuff that needs to be rewritten here. I'm going to make a "purge queue" PR to hash out the purge queue definition, and I will also make a grammar-and-elegance pass. This suggestion will be incorporated into that latter PR. As always, good catch.

dparmar18 · 2024-12-23T12:14:28Z

From what I understand is - @zdover23 will take care of all the grammar and touch ups in this PR but just FYI we'd still need an approval from @ceph/cephfs to validate the content credibility.

zdover23 · 2024-12-23T12:18:36Z

From what I understand is - @zdover23 will take care of all the grammar and touch ups in this PR but just FYI we'd still need an approval from @ceph/cephfs to validate the content credibility.

@dparmar18, This is correct. If you get someone from CephFS to verify the technical accuracy of this content, I will merge this PR and raise a new PR in which I will clean the English and make sure that the RST file is ready to be backported to release branches. @vshankar, could you assign someone to check the technical accuracy of the information added to the docs in this PR?

vshankar · 2024-12-23T13:29:57Z

From what I understand is - @zdover23 will take care of all the grammar and touch ups in this PR but just FYI we'd still need an approval from @ceph/cephfs to validate the content credibility.

@dparmar18, This is correct. If you get someone from CephFS to verify the technical accuracy of this content, I will merge this PR and raise a new PR in which I will clean the English and make sure that the RST file is ready to be backported to release branches. @vshankar, could you assign someone to check the technical accuracy of the information added to the docs in this PR?

I will have a look at this now.

zdover23 · 2024-12-23T13:30:55Z

From what I understand is - @zdover23 will take care of all the grammar and touch ups in this PR but just FYI we'd still need an approval from @ceph/cephfs to validate the content credibility.

@dparmar18, This is correct. If you get someone from CephFS to verify the technical accuracy of this content, I will merge this PR and raise a new PR in which I will clean the English and make sure that the RST file is ready to be backported to release branches. @vshankar, could you assign someone to check the technical accuracy of the information added to the docs in this PR?

I will have a look at this now.

Cool.

vshankar · 2024-12-23T16:14:45Z

doc/cephfs/purge-queue.rst

+
+.. note:: Generally, the defaults are adequate for most clusters. However, in
+          case of huge clusters, if the need arises, values might be tuned to
+          4-5 times of the default value as a starting point and further 


4x-5x for all the above configurations?

You should also provide a sample configuration.

4x-5x for all the above configurations?

So, the users can start with the most basic one i.e. setting filer_max_purge_ops to 40-50 which mostly should work. If it doesn't then rest three mentioned above can be tuned to 4x-5x.

You should also provide a sample configuration.

I can but it's usually just one or two conf val changes (as I mentioned above). Do you want me to add example of how it's done in the doc?

Yeh, I think so. Providing a sample would help users not to second guess. The configs may not be perfect for their cluster, but it provides an understanding of what all to change.

Yeh, I think so. Providing a sample would help users not to second guess. The configs may not be perfect for their cluster, but it provides an understanding of what all to change.

Added some examples, PTAL.

doc/cephfs/purge-queue.rst

vshankar · 2024-12-23T16:22:29Z

doc/cephfs/purge-queue.rst

+
+When a client requests deletion of a directory (say ``rm -rf``):
+
+- MDS queues the files and subdirectories (purge items) from journal in the


So, there is a purge queue journal (pq). Its a bit unclear which journal is being referred to here.

The journal here comes from osdc/Journaler.h". Since this is MDS's side, would it be correct to call it MDS Journal?

So, there is MDS metadata journal (mdlog) and the MDS purge queue journal (pq). Both of course use osdc/Journaler.h class, but my question here is which of the above two journals is being referred.

It's purge queue journal

ceph/src/mds/PurgeQueue.cc

Lines 129 to 131 in 5061b31

journaler("pq", MDS_INO_PURGE_QUEUE + rank, metadata_pool,

CEPH_FS_ONDISK_MAGIC, objecter_, nullptr, 0,

&finisher),

Right. So, let's mention that explicitly in the doc.

@vshankar, I'll get this in the document when I get back to my office. It'll be in today.

At ease @zdover23. I have requested one small update from @dparmar18 and then its good to go 👍

Roger wilco, @vshankar.

@vshankar PTAL

dparmar18 · 2024-12-24T12:52:27Z

@zdover23 made some minor changes and fixes while also adding some more content i felt was necessary. PTAL https://github.com/ceph/ceph/compare/ddd994291dba374fe122a7d59dfc3835fe665356..65bd5c2f0e08c68f18e02e0c21466bdd8fa4c8ee

zdover23 · 2024-12-24T12:53:26Z

@zdover23 made some minor changes and fixes while also adding some more content i felt was necessary. PTAL https://github.com/ceph/ceph/compare/ddd994291dba374fe122a7d59dfc3835fe665356..65bd5c2f0e08c68f18e02e0c21466bdd8fa4c8ee

@dparmar18 I'm on it.

dparmar18 · 2024-12-24T12:54:18Z

oh shoot while resolving conflicts, i messed up this part:

.. confval:: filer_max_purge_ops 
.. confval:: mds_max_purge_files
.. confval:: mds_max_purge_ops
.. confval:: mds_max_purge_ops_per_pg

- filer_max_purge_ops (default 10)
- mds_max_purge_files (default 64)
- mds_max_purge_ops (default 8192)
- mds_max_purge_ops_per_pg (default 0.5)

dparmar18 · 2024-12-24T12:57:11Z

oh shoot while resolving conflicts, i messed up this part:

.. confval:: filer_max_purge_ops 
.. confval:: mds_max_purge_files
.. confval:: mds_max_purge_ops
.. confval:: mds_max_purge_ops_per_pg

- filer_max_purge_ops (default 10)
- mds_max_purge_files (default 64)
- mds_max_purge_ops (default 8192)
- mds_max_purge_ops_per_pg (default 0.5)

removed redundant entries. https://github.com/ceph/ceph/compare/65bd5c2f0e08c68f18e02e0c21466bdd8fa4c8ee..611478de3af6a38c593949cc3101d14a3e549311

zdover23 · 2024-12-24T13:07:18Z

oh shoot while resolving conflicts, i messed up this part:
.. confval:: filer_max_purge_ops 
.. confval:: mds_max_purge_files
.. confval:: mds_max_purge_ops
.. confval:: mds_max_purge_ops_per_pg

- filer_max_purge_ops (default 10)
- mds_max_purge_files (default 64)
- mds_max_purge_ops (default 8192)
- mds_max_purge_ops_per_pg (default 0.5)
removed redundant entries. https://github.com/ceph/ceph/compare/65bd5c2f0e08c68f18e02e0c21466bdd8fa4c8ee..611478de3af6a38c593949cc3101d14a3e549311

@dparmar18 Just add the information that Venky asked for, and I'll make sure that this builds correctly. Let me know when it's ready for me to fix up.

Fixes: https://tracker.ceph.com/issues/68571 Signed-off-by: Dhairya Parmar <[email protected]>

vshankar

Good start documenting this. Nice work @dparmar18

@zdover23 FYI

zdover23 · 2024-12-30T06:19:13Z

Good start documenting this. Nice work @dparmar18

@zdover23 FYI

@vshankar, Which release branches should I backport this change to?

vshankar · 2024-12-30T06:21:20Z

Good start documenting this. Nice work @dparmar18
@zdover23 FYI

@vshankar, Which release branches should I backport this change to?

Updated the tracker - quincy,reef,squid

zdover23 · 2024-12-30T07:32:28Z

#61193 - Squid backport
#61194 - Reef backport
#61195 - Quincy backport

github-actions bot added cephfs Ceph File System documentation labels Nov 21, 2024

dparmar18 force-pushed the wip-68571 branch from 4756cea to 5f59b9f Compare November 25, 2024 13:28

dparmar18 marked this pull request as ready for review November 25, 2024 13:29

dparmar18 requested a review from a team as a code owner November 25, 2024 13:29

dparmar18 requested a review from a team November 25, 2024 13:29

anthonyeleven approved these changes Nov 25, 2024

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joscollin reviewed Nov 28, 2024

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zdover23 force-pushed the wip-68571 branch from ed3674b to ddd9942 Compare December 20, 2024 01:09

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dparmar18 force-pushed the wip-68571 branch from ddd9942 to 65bd5c2 Compare December 24, 2024 12:50

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zdover23 force-pushed the wip-68571 branch from 611478d to 0230a8b Compare December 25, 2024 09:40

doc/cephfs: document purge queue and its perf counters

ae92773

Fixes: https://tracker.ceph.com/issues/68571 Signed-off-by: Dhairya Parmar <[email protected]>

dparmar18 force-pushed the wip-68571 branch from 0230a8b to ae92773 Compare December 26, 2024 06:39

zdover23 requested a review from vshankar December 27, 2024 13:18

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vshankar approved these changes Dec 30, 2024

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zdover23 merged commit ff1134f into ceph:main Dec 30, 2024


		When a client requests deletion of a directory (say ``rm -rf``):

		- MDS queues the files and subdirectories (purge items) from journal in the

	journaler("pq", MDS_INO_PURGE_QUEUE + rank, metadata_pool,
	CEPH_FS_ONDISK_MAGIC, objecter_, nullptr, 0,
	&finisher),

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