linux-kernel - Re: [PATCHSET v6 0/12] Uncached buffered IO

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Message-ID: <668f271f-dc44-49e1-b8dc-08e65e1fec23@kernel.dk>
Date: Tue, 3 Dec 2024 14:06:27 -0700
From: Jens Axboe <axboe@...nel.dk>
To: "Christoph Lameter (Ampere)" <cl@...two.org>
Cc: linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, hannes@...xchg.org,
 clm@...a.com, linux-kernel@...r.kernel.org, willy@...radead.org,
 kirill@...temov.name, bfoster@...hat.com
Subject: Re: [PATCHSET v6 0/12] Uncached buffered IO

On 12/3/24 11:23 AM, Christoph Lameter (Ampere) wrote:
> On Tue, 3 Dec 2024, Jens Axboe wrote:
> 
>>
>> So here's a new approach to the same concent, but using the page cache
>> as synchronization. That makes RWF_UNCACHED less special, in that it's
>> just page cache IO, except it prunes the ranges once IO is completed.
> 
> 
> Great idea and someting that is really important these days.
> 
> However, one nit that I have is the use of the term "uncached" for a
> folio/page. An uncached "page frame" refers to a page frame that requires
> accesses not  going through the cpu cache. I.e. device mappings. This is
> an established mm/cpu term as far as I can tell.
> 
> So maybe be a bit more specific about which cache this is?
> 
> PAGE_CACHE_UNCACHED?
> 
> or use a different term. It is cached after all but only for a brief
> period. So this may be a "TEMPORAL_PAGE" or so? (Similar to the x86
> "non-temporal" stores).

I actually did consider using some form of temporal, as it's the only
other name I liked. But I do think cached_uncached becomes pretty
unwieldy. Which is why I just stuck with uncached. Yes I know it means
different things in different circles, but probably mostly an overlap
with deeper technical things like that. An honestly almost impossible to
avoid overlap these days, everything has been used already :-)

IOW, I think uncached is probably still the most descriptive thing out
there, even if I'm certainly open to entertaining other names. Just not
anything yet that has really resonated with me.

-- 
Jens Axboe