linux-kernel - Re: [PATCH 6/7] mm: folio_may_be_cached() unless folio_test

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Message-ID: <2ba8984b-8818-2a7f-7544-4c5fce3e0878@google.com>
Date: Mon, 8 Sep 2025 13:04:39 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: David Hildenbrand <david@...hat.com>
cc: Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
    Will Deacon <will@...nel.org>, Shivank Garg <shivankg@....com>, 
    Matthew Wilcox <willy@...radead.org>, 
    Christoph Hellwig <hch@...radead.org>, Keir Fraser <keirf@...gle.com>, 
    Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>, 
    Frederick Mayle <fmayle@...gle.com>, Peter Xu <peterx@...hat.com>, 
    "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>, 
    Johannes Weiner <hannes@...xchg.org>, Vlastimil Babka <vbabka@...e.cz>, 
    Alexander Krabler <Alexander.Krabler@...a.com>, 
    Ge Yang <yangge1116@....com>, Li Zhe <lizhe.67@...edance.com>, 
    Chris Li <chrisl@...nel.org>, Yu Zhao <yuzhao@...gle.com>, 
    Axel Rasmussen <axelrasmussen@...gle.com>, 
    Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>, 
    Konstantin Khlebnikov <koct9i@...il.com>, linux-kernel@...r.kernel.org, 
    linux-mm@...ck.org
Subject: Re: [PATCH 6/7] mm: folio_may_be_cached() unless
 folio_test_large()

On Mon, 8 Sep 2025, David Hildenbrand wrote:
> On 08.09.25 13:19, Hugh Dickins wrote:
...
> > 
> > (Settimg aside that I've never perceived those pagevecs/batches as a
> > "cache"; but lru_cache_disable() gave us that terminology, and we've
> > gone with the flow ever since.  lru_add_drain() would be better named
> > lru_cache_drain() now, I've always got hung up on "adding a drain".)
> 
> Yeah, the terminology is not that intuitive :)
> 
> Not sure if using "batched" instead of "cached" might be clearer long-term?
> 
> > 
> > "may be" rather than "maybe" was intentional: perhaps too subtle,
> > but to a native speaker it neatly expresses both the "we can do this"
> > and "might this have been done" cases.
> 
> I would wish we could find something that also non-native speakers can
> immediately understand ;)
> 
> "may_get_lru_cached" / "may_get_lru_batched"?
> 
> /me could not even phrase it in German properly
> 
> > 
> > kernel-doc?  I don't think so, this is very much an mm-internal
> > matter, and I don't care for the way kernel-doc forces us towards
> > boilerplate ("@folio: The folio.") rather than helpful comment.
> 
> So a comment that this is an internal helper might be nice. Or we just move it
> straight to mm/internal.h ?

mm/internal.h, where we hide things (GFP_RECLAIM_MASK etc!) that belong
elsewhere?  No thanks.

David, I think you're over-thinking this: I'm coming to regret not just
going with your excellent folio_test_large() optimization, and let
someone else mess around with the naming.

I'll post later with my current naming, but if it's the
Suggested-by that's making you uncomfortable, we can delete it.

Hugh