linux-kernel - Re: [RESEND PATCH v7 00/10] Small-sized THP for anonymous memory

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Date:   Tue, 28 Nov 2023 12:15:30 +0000
From:   Ryan Roberts <ryan.roberts@....com>
To:     David Hildenbrand <david@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Alistair Popple <apopple@...dia.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v7 00/10] Small-sized THP for anonymous memory

On 28/11/2023 08:48, David Hildenbrand wrote:
> 
>>>
>>> Agreed. We are bikeshedding here. But if we really can't swallow "small-sized
>>> THP" then perhaps the most efficient way to move this forwards is to review the
>>> documentation (where "small-sized THP" appears twice in order to differentiate
>>> from PMD-sized THP) - its in patch 3. Perhaps it will be easier to come up with
>>> a good description in the context of those prose? Then once we have that,
>>> hopefully a term will fall out that I'll update the commit logs with.
>>>
>>
>> I will see you over in patch 3, then. I've already looked at it and am going
>> to suggest a long and a short name. The long name is for use in comments and
>> documentation, and the short name is for variable fragments:
>>
>>       Long name:  "pte-mapped THPs"
>>       Short names: pte_thp, or pte-thp
> 
> The issue is that any THP can be pte-mapped, even a PMD-sized THP. However, the
> "natural" way to map a PMD-sized THP is using a PMD.
> 

How about we just stop trying to come up with a term for the "small-sized THP"
vs "PMD-sized THP" and instead invent a name that covers ALL THP:

"multi-size THP" vs "PMD-sized THP".

Then in the docs we can talk about how multi-size THP introduces the ability to
allocate memory in blocks that are bigger than a base page but smaller than
traditional PMD-size, in increments of a power-of-2 number of pages.