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Message-ID: <15b067d7-8f95-d409-64be-d22359f0942a@redhat.com>
Date: Fri, 15 Sep 2023 17:43:20 +0200
From: David Hildenbrand <david@...hat.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Daniel Gomez <da.gomez@...sung.com>,
"minchan@...nel.org" <minchan@...nel.org>,
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Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH 0/6] shmem: high order folios support in write path
On 15.09.23 17:40, Matthew Wilcox wrote:
> On Fri, Sep 15, 2023 at 05:36:27PM +0200, David Hildenbrand wrote:
>> On 15.09.23 17:34, Matthew Wilcox wrote:
>>> No, it can't. This patchset triggers only on write, not on read or page
>>> fault, and it's conservative, so it will only allocate folios which are
>>> entirely covered by the write. IOW this is memory we must allocate in
>>> order to satisfy the write; we're just allocating it in larger chunks
>>> when we can.
>>
>> Oh, good! I was assuming you would eventually over-allocate on the write
>> path.
>
> We might! But that would be a different patchset, and it would be
> subject to its own discussion.
>
> Something else I've been wondering about is possibly reallocating the
> pages on a write. This would apply to both normal files and shmem.
> If you read in a file one byte at a time, then overwrite a big chunk of
> it with a large single write, that seems like a good signal that maybe
> we should manage that part of the file as a single large chunk instead
> of individual pages. Maybe.
>
> Lots of things for people who are obsessed with performance to play
> with ;-)
:) Absolutely. ... because if nobody will be consuming that written
memory any time soon, it might also be the wrong place for a large/huge
folio.
--
Cheers,
David / dhildenb
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