From: Nick Piggin <npiggin@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [patch] radix-tree: use indirect bit
Date: Tue, 7 Aug 2007 04:51:20 +0200 [thread overview]
Message-ID: <20070807025120.GD17986@wotan.suse.de> (raw)
In-Reply-To: <20070806114055.704b78d8.akpm@linux-foundation.org>
On Mon, Aug 06, 2007 at 11:40:55AM -0700, Andrew Morton wrote:
> On Thu, 2 Aug 2007 07:24:46 +0200 Nick Piggin <npiggin@suse.de> wrote:
>
> > Rather than sign direct radix-tree pointers with a special bit, sign
> > the indirect one that hangs off the root. This means that, given a
> > lookup_slot operation, the invalid result will be differentiated from
> > the valid (previously, valid results could have the bit either set or
> > clear).
> >
> > This does not affect slot lookups which occur under lock -- they
> > can never return an invalid result. Is needed in future for lockless
> > pagecache.
>
> so.. we added 30 bytes of text to radix-tree.o for no purpose?
I guess no functional purpose at this stage. But I do like this
scheme better anyway, because it means that locked API users are
never exposed to the direct/indirect bit.
It's a bit variable... on powerpc, it _removed_ 22 bytes, and if
I delete the extra BUG_ON that I introduced, then it removes 128
bytes.
prev parent reply other threads:[~2007-08-07 2:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-02 5:24 [patch] radix-tree: use indirect bit Nick Piggin
2007-08-02 7:13 ` Peter Zijlstra
2007-08-06 18:40 ` Andrew Morton
2007-08-07 2:51 ` Nick Piggin [this message]
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=20070807025120.GD17986@wotan.suse.de \
--to=npiggin@suse.de \
--cc=a.p.zijlstra@chello.nl \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.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