From: "Arnaldo Carvalho de Melo" <acme@redhat.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Daniel Drake <dsd@gentoo.org>,
linux-kernel@vger.kernel.org, davem@davemloft.net,
kune@deine-taler.de
Subject: Re: [RFC] Documentation about unaligned memory access
Date: Mon, 26 Nov 2007 22:40:16 -0200 [thread overview]
Message-ID: <20071127004016.GD4684@ghostprotocols.net> (raw)
In-Reply-To: <1196088427.4149.262.camel@johannes.berg>
Em Mon, Nov 26, 2007 at 03:47:06PM +0100, Johannes Berg escreveu:
>
> > Sidenote: in the above example, you may wish to reorder the fields in the
> > above structure so that the overall structure uses less memory. For example,
> > moving field3 to sit inbetween field1 and field2 (where the padding is
> > inserted) would shrink the overall structure by 1 byte:
> >
> > struct foo {
> > u16 field1;
> > u8 field3;
> > u32 field2;
> > };
>
> You can reorder to u32, u16, u8 order and save another byte :)
>
> A reference to pahole could be appropriate here, and probably a small
> note that some large existing structures like netdev have deliberate
> holes to achieve cache alignment.
shameless plug:
https://ols2006.108.redhat.com/2007/Reprints/melo-Reprint.pdf
- Arnaldo
next prev parent reply other threads:[~2007-11-27 0:40 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-23 0:15 [RFC] Documentation about unaligned memory access Daniel Drake
2007-11-23 0:27 ` Avuton Olrich
2007-11-23 1:29 ` Alan Cox
2007-11-23 3:04 ` Kyle Moffett
2007-11-23 6:18 ` dean gaudet
2007-11-23 9:46 ` Arne Georg Gleditsch
2007-11-26 14:50 ` dean gaudet
2007-11-23 1:29 ` David Miller
2007-11-23 10:06 ` Jan Engelhardt
2007-11-23 11:43 ` Heikki Orsila
2007-11-25 11:16 ` Geert Uytterhoeven
2007-11-25 11:24 ` Heikki Orsila
2007-11-26 0:48 ` Alan Cox
2007-11-26 17:12 ` Ben Dooks
2007-11-27 7:51 ` Kumar Gala
2007-11-23 22:02 ` Vadim Lobanov
2007-11-23 22:52 ` Dmitri Vorobiev
2007-11-24 13:34 ` Pierre Ossman
2007-11-24 15:50 ` Luciano Rocha
2007-11-24 16:19 ` Pierre Ossman
2007-11-24 17:22 ` Luciano Rocha
2007-11-24 17:35 ` Pierre Ossman
2007-11-24 18:28 ` Luciano Rocha
2007-11-24 17:53 ` Haavard Skinnemoen
2007-11-25 8:27 ` Denys Vlasenko
2007-11-25 14:13 ` Olaf Titz
2007-11-26 9:14 ` DM
2007-11-26 14:47 ` Johannes Berg
2007-11-27 0:40 ` Arnaldo Carvalho de Melo [this message]
2007-11-26 14:51 ` Johannes Berg
2007-11-30 8:18 ` Jörn Engel
[not found] <fa.U+CIv4JClOmn6KppLkEOSk7RW0Y@ifi.uio.no>
2007-11-23 1:24 ` Robert Hancock
2007-11-23 2:07 ` Andi Kleen
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