From: akpm@linux-foundation.org (Andrew Morton)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC] change non-atomic bitops method
Date: Tue, 3 Feb 2015 00:48:41 -0800 [thread overview]
Message-ID: <20150203004841.b48e84df.akpm@linux-foundation.org> (raw)
In-Reply-To: <20150203.004031.593368249759204527.davem@davemloft.net>
On Tue, 03 Feb 2015 00:40:31 -0800 (PST) David Miller <davem@davemloft.net> wrote:
> From: Andrew Morton <akpm@linux-foundation.org>
> Date: Mon, 2 Feb 2015 22:38:51 -0800
>
> > It is only with both these ratios that we can work out whether the
> > patch is a net gain. My suspicion is that set_bit on an already-set
> > bit is so rare that the patch will be a loss.
>
> A common pattern is implementing a "referenced" bit, and in that case
> the bit is often already set, and in such a scenerio the proposed
> change is a huge win.
pagecache, dcache and icache already perform this optimisation (and
only pagecache uses bitops for it anyway). I'm not sure what's left.
But there's really no point in speculating about this - it's trivial to
instrument the kernel and get real numbers.
next prev parent reply other threads:[~2015-02-03 8:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-02 3:55 [RFC] change non-atomic bitops method Wang, Yalin
2015-02-02 18:53 ` Laura Abbott
2015-02-02 19:31 ` Uwe Kleine-König
2015-02-02 23:29 ` Andrew Morton
2015-02-02 23:31 ` Russell King - ARM Linux
2015-02-03 1:17 ` Kirill A. Shutemov
2015-02-03 2:13 ` Wang, Yalin
2015-02-03 5:42 ` Wang, Yalin
2015-02-03 6:38 ` Andrew Morton
2015-02-03 7:03 ` Wang, Yalin
2015-02-03 8:42 ` Wang, Yalin
2015-02-03 10:59 ` Andrew Morton
2015-02-09 8:18 ` Wang, Yalin
2015-02-09 20:34 ` Andrew Morton
2015-02-10 7:05 ` Wang, Yalin
2015-02-09 21:42 ` Rasmus Villemoes
2015-02-03 8:40 ` David Miller
2015-02-03 8:48 ` Andrew Morton [this message]
2015-02-03 9:34 ` Rasmus Villemoes
2015-02-03 9:41 ` Wang, Yalin
2015-02-03 10:39 ` Kirill A. Shutemov
2015-02-03 15:14 ` David Howells
2015-02-03 19:10 ` Uwe Kleine-König
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=20150203004841.b48e84df.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=linux-arm-kernel@lists.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;
as well as URLs for NNTP newsgroup(s).