linux-kernel - Re: [PATCH v2] Documentation/cgroup-v2: Update memory.{stat,numa_stat} description to reflect possible units

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Message-ID: <8d2d3903-aab2-4f38-b3ad-6adf7b0fc9ad@fujitsu.com>
Date: Fri, 17 Jan 2025 03:09:59 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: Tejun Heo <tj@...nel.org>
CC: Jonathan Corbet <corbet@....net>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, Johannes Weiner <hannes@...xchg.org>,
	"mkoutny@...e.com" <mkoutny@...e.com>, "cgroups@...r.kernel.org"
	<cgroups@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Waiman Long <llong@...hat.com>
Subject: Re: [PATCH v2] Documentation/cgroup-v2: Update
 memory.{stat,numa_stat} description to reflect possible units

+

On 17/01/2025 01:19, Tejun Heo wrote:
> Hello,
> 
> On Thu, Jan 16, 2025 at 05:50:54AM +0000, Zhijian Li (Fujitsu) wrote:
> ...
>> Let me quote a piece of the numa.stat:
>>
>> In pages:
>>>           pgdemote_khugepaged
>>>                 Number of pages demoted by khugepaged.
> 
> If this is the only entry in pages, I'm not sure the proposed document
> update is the best one. 

I asked the ChatGPT with the contents in memory.stat, the ChatGPT answered:
In short, There are 28 entries in bytes and 37 entries in pages.

```
Based on the list provided, here are the counts for each:

### Entries in Bytes

There are 28 entries in bytes:

1. anon
2. file
3. kernel
4. kernel_stack
5. pagetables
6. sec_pagetables
7. percpu
8. sock
9. vmalloc
10. shmem
11. zswap
12. zswapped
13. file_mapped
14. file_dirty
15. file_writeback
16. swapcached
17. anon_thp
18. file_thp
19. shmem_thp
20. inactive_anon
21. active_anon
22. inactive_file
23. active_file
24. unevictable
25. slab_reclaimable
26. slab_unreclaimable
27. slab
28. hugetlb

### Entries in Pages

There are 37 entries in pages:

1. workingset_refault_anon
2. workingset_refault_file
3. workingset_activate_anon
4. workingset_activate_file
5. workingset_restore_anon
6. workingset_restore_file
7. workingset_nodereclaim
8. pgscan
9. pgsteal
10. pgscan_kswapd
11. pgscan_direct
12. pgscan_khugepaged
13. pgsteal_kswapd
14. pgsteal_direct
15. pgsteal_khugepaged
16. pgfault
17. pgmajfault
18. pgrefill
19. pgactivate
20. pgdeactivate
21. pglazyfree
22. pglazyfreed
23. swpin_zero
24. swpout_zero
25. zswpin
26. zswpout
27. zswpwb
28. thp_fault_alloc
29. thp_collapse_alloc
30. thp_swpout
31. thp_swpout_fallback
32. numa_pages_migrated
33. numa_pte_updates
34. numa_hint_faults
35. pgdemote_kswapd
36. pgdemote_direct
37. pgdemote_khugepaged

```


The above can have an easy alternative description
> "the number of times khugepaged demoted a huge page" - ie. indicate that it
> is an event counter instead, which is a plausible and likely more intuitive
> definition anyway given that a "huge page" can plausibly be of different
> sizes. With the key name and matching description, I'm not sure it's
> violating the rule that all *sizes* are expressed in bytes.
> 
> Thanks.
>