linux-kernel - Re: [PATCH 0/2] mm: introduce per-order mTHP split counters

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Date: Wed, 24 Apr 2024 17:29:02 +0200
From: David Hildenbrand <david@...hat.com>
To: Ryan Roberts <ryan.roberts@....com>, Lance Yang <ioworker0@...il.com>,
 akpm@...ux-foundation.org
Cc: 21cnbao@...il.com, baolin.wang@...ux.alibaba.com,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/2] mm: introduce per-order mTHP split counters

On 24.04.24 17:20, Ryan Roberts wrote:
> On 24/04/2024 16:00, David Hildenbrand wrote:
>> On 24.04.24 15:51, Lance Yang wrote:
>>> Hi all,
>>>
>>> At present, the split counters in THP statistics no longer include
>>> PTE-mapped mTHP. Therefore, we want to introduce per-order mTHP split
>>> counters to monitor the frequency of mTHP splits. This will assist
>>> developers in better analyzing and optimizing system performance.
>>>
>>> /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats
>>>           split_page
>>>           split_page_failed
>>>           deferred_split_page
>>>
>>> Thanks,
>>> Lance
>>> ---
>>>
>>> Lance Yang (2):
>>>    mm: add per-order mTHP split counters
>>>    mm: add docs for per-order mTHP split counters
>>>
>>>    Documentation/admin-guide/mm/transhuge.rst | 16 ----------------
>>
>> We really have to start documenting these, and what the sementics are.
> 
> I think the diffstat is backwards; the series definitely adds more lines than it
> removes. And patch 2 is adding 16 lines of docs, not removing them. How are you
> generating this? `git format-patch` should do it correctly for you.
> 
>>
>> E.g., is split_page_failed contained in split_page? Is deferred_split_page
>> contained in split_page?
>>
>> But also: just don't call it "split_page". Drop the "_page".
>>
>> split
>> split_failed
>> split_deferred
> 
> I guess we are back in "should we be consistent with the existing vmstats"
> territory, which uses split_page/split_page_failed/deferred_split_page
> 

Yeah, "thp_split_page" really is odd "transparent huge page split page".

> But here, I agree that dropping _page is nicer.
Right; we also shouldn't call it "thp_split_page" here :)

-- 
Cheers,

David / dhildenb