From: Linus Torvalds <torvalds@linux-foundation.org>
To: Kiryl Shutsemau <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: Optimizing small reads
Date: Tue, 7 Oct 2025 15:35:27 -0700 [thread overview]
Message-ID: <CAHk-=wiTqdaadro3ACg6vJWtazNn6sKyLuHHMn=1va2+DVPafw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wjDvkQ9H9kEv-wWKTzdBsnCWpwgnvkaknv4rjSdLErG0g@mail.gmail.com>
On Tue, 7 Oct 2025 at 14:47, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Note: this also ends up doing it all with pagefaults disabled, becasue
> that way we can do the looping without dropping and re-taking the RCU
> lock. I'm not sure that is sensible, but whatever. Considering that I
> didn't test this AT ALL, please just consider this a "wild handwaving"
> patch.
It might be worth noting that the real reason for disabling page
faults is that I think the whole loop should be moved into
filemap_fast_read(), and then the sequence count read - with the
memory barrier - would be done only once.
Plus at that point the code can do the page lookup only once too.
So that patch is not only untested, it's also just a "step one".
But I think I'll try to boot it next. Wish me luck.
Linus
next prev parent reply other threads:[~2025-10-07 22:35 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-03 2:18 Linus Torvalds
2025-10-03 3:32 ` Luis Chamberlain
2025-10-15 21:31 ` Swarna Prabhu
2025-10-03 9:55 ` Kiryl Shutsemau
2025-10-03 16:18 ` Linus Torvalds
2025-10-03 16:40 ` Linus Torvalds
2025-10-03 17:23 ` Kiryl Shutsemau
2025-10-03 17:49 ` Linus Torvalds
2025-10-06 11:44 ` Kiryl Shutsemau
2025-10-06 15:50 ` Linus Torvalds
2025-10-06 18:04 ` Kiryl Shutsemau
2025-10-06 18:14 ` Linus Torvalds
2025-10-07 21:47 ` Linus Torvalds
2025-10-07 22:35 ` Linus Torvalds [this message]
2025-10-07 22:54 ` Linus Torvalds
2025-10-07 23:30 ` Linus Torvalds
2025-10-08 14:54 ` Kiryl Shutsemau
2025-10-08 16:27 ` Linus Torvalds
2025-10-08 17:03 ` Linus Torvalds
2025-10-09 16:22 ` Kiryl Shutsemau
2025-10-09 17:29 ` Linus Torvalds
2025-10-10 10:10 ` Kiryl Shutsemau
2025-10-10 17:51 ` Linus Torvalds
2025-10-13 15:35 ` Kiryl Shutsemau
2025-10-13 15:39 ` Kiryl Shutsemau
2025-10-13 16:19 ` Linus Torvalds
2025-10-14 12:58 ` Kiryl Shutsemau
2025-10-14 16:41 ` Linus Torvalds
2025-10-13 16:06 ` Linus Torvalds
2025-10-13 17:26 ` Theodore Ts'o
2025-10-14 3:20 ` Theodore Ts'o
2025-10-08 10:28 ` Kiryl Shutsemau
2025-10-08 16:24 ` Linus Torvalds
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAHk-=wiTqdaadro3ACg6vJWtazNn6sKyLuHHMn=1va2+DVPafw@mail.gmail.com' \
--to=torvalds@linux-foundation.org \
--cc=kirill@shutemov.name \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mcgrof@kernel.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox