From: Matt Mackall <mpm@selenic.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Jens Axboe <jens.axboe@oracle.com>,
Linux Kernel Development <linux-kernel@vger.kernel.org>,
mingo@elte.hu, Linux/m68k <linux-m68k@vger.kernel.org>
Subject: Re: [PATCH 09/10] Change table chaining layout
Date: Mon, 22 Oct 2007 15:38:48 -0500 [thread overview]
Message-ID: <20071022203848.GI17536@waste.org> (raw)
In-Reply-To: <20071022211617.31f5c63d@the-village.bc.nu>
On Mon, Oct 22, 2007 at 09:16:17PM +0100, Alan Cox wrote:
> On Mon, 22 Oct 2007 12:49:40 -0700 (PDT)
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> >
> >
> > On Mon, 22 Oct 2007, Geert Uytterhoeven wrote:
> > >
> > > Better safe than sorry...
> > >
> > > Is it possible that a chain entry pointer has bit 1 set on architectures
> > > (e.g. m68k) where the natural alignment of 32-bit quantities is _2_ bytes,
> > > not 4?
> >
> > Better make sure that such alignment never happens... But no, I don't
> > think it will, since these things would generally always have to be
> > allocated with an allocator, and the *allocator* won't return 2-byte
> > aligned data structures.
>
> No - but a structure which has other objects in it before the object
> being written out may well be 2 byte aligned on M68K and some of the
> other externally 16bit platforms - ditto local dynamic objects.
Also, the current version of SLOB will return objects aligned at 2 bytes if the
architecture allows it.
> Why can't we just make the list one item longer than the entry count and
> stick a NULL on the end of it like normal people ? Then you need one bit
> which ought to be safe for everyone (and if the bit is a macro any CPU
> warped enough to have byte alignment is surely going to have top bits
> spare...)
I'm guessing the extra entry makes slab-like allocators unhappy.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2007-10-22 20:40 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-22 18:10 [PATCH 00/10] SG updates Jens Axboe
2007-10-22 18:10 ` [PATCH 01/10] [SG] Add helpers for manipulating SG entries Jens Axboe
2007-10-22 18:10 ` [PATCH 02/10] [SG] Update block layer to use sg helpers Jens Axboe
2007-10-23 5:13 ` Heiko Carstens
2007-10-23 5:16 ` Jens Axboe
2007-10-23 5:42 ` [PATCH] fix ll_rw_blk.c build on s390 Heiko Carstens
2007-10-23 5:44 ` [PATCH] net: fix xfrm build - missing scatterlist.h include Heiko Carstens
2007-10-23 7:28 ` Jens Axboe
2007-10-23 14:32 ` [PATCH 02/10] [SG] Update block layer to use sg helpers John Stoffel
2007-10-22 18:10 ` [PATCH 03/10] [SG] Update crypto/ to " Jens Axboe
2007-10-22 18:10 ` [PATCH 04/10] [SG] Update drivers to use " Jens Axboe
2007-10-23 6:28 ` Heiko Carstens
2007-10-23 7:14 ` Jens Axboe
2007-10-23 7:16 ` Heiko Carstens
2007-10-22 18:10 ` [PATCH 05/10] [SG] Update fs/ " Jens Axboe
2007-10-22 18:11 ` [PATCH 06/10] [SG] Update net/ " Jens Axboe
2007-10-23 10:44 ` Christian Borntraeger
2007-10-23 10:45 ` Jens Axboe
2007-10-22 18:11 ` [PATCH 07/10] [SG] Update swiotlb " Jens Axboe
2007-10-22 18:11 ` [PATCH 08/10] [SG] Update arch/ " Jens Axboe
2007-10-22 21:10 ` Benny Halevy
2007-10-23 7:26 ` Jens Axboe
2007-10-22 18:11 ` [PATCH 09/10] Change table chaining layout Jens Axboe
2007-10-22 19:39 ` Geert Uytterhoeven
2007-10-22 19:49 ` Linus Torvalds
2007-10-22 19:52 ` Jens Axboe
2007-10-22 20:16 ` Alan Cox
2007-10-22 20:38 ` Matt Mackall [this message]
2007-10-22 20:44 ` Linus Torvalds
2007-10-22 21:43 ` Alan Cox
2007-10-22 21:47 ` Linus Torvalds
2007-10-23 0:07 ` David Miller
2007-10-23 7:18 ` Geert Uytterhoeven
2007-10-23 9:29 ` Boaz Harrosh
2007-10-23 9:41 ` Jens Axboe
2007-10-23 9:50 ` Boaz Harrosh
2007-10-23 9:55 ` Jens Axboe
2007-10-23 10:23 ` Boaz Harrosh
2007-10-23 10:29 ` Jens Axboe
2007-10-23 15:22 ` Linus Torvalds
2007-10-24 8:05 ` Jens Axboe
2007-10-24 9:03 ` Geert Uytterhoeven
2007-10-24 9:12 ` Jens Axboe
2007-10-24 13:35 ` Olivier Galibert
2007-10-24 13:38 ` Jens Axboe
2007-10-24 13:45 ` Olivier Galibert
2007-10-24 15:16 ` Linus Torvalds
2007-10-25 8:40 ` Rusty Russell
2007-10-25 9:11 ` Jens Axboe
2007-10-25 11:54 ` Rusty Russell
2007-10-26 0:03 ` Rusty Russell
2007-10-25 15:40 ` Linus Torvalds
2007-10-25 16:03 ` Benny Halevy
2007-10-26 5:01 ` Paul Mackerras
2007-10-26 14:52 ` Linus Torvalds
2007-10-26 17:28 ` Jens Axboe
2007-11-05 6:11 ` [RFC PATCH 1/2] sg_ring instead of scatterlist chaining Rusty Russell
2007-11-05 6:15 ` [RFC PATCH 2/2] sg_ring instead of scatterlist chaining in virtio Rusty Russell
2007-11-05 16:40 ` [RFC PATCH 1/2] sg_ring instead of scatterlist chaining Randy Dunlap
2007-10-23 10:33 ` [PATCH 09/10] Change table chaining layout Ingo Molnar
2007-10-23 10:56 ` Jens Axboe
2007-10-23 11:27 ` Ingo Molnar
2007-10-23 19:23 ` Geert Uytterhoeven
2007-10-23 21:46 ` Jens Axboe
2007-10-24 6:56 ` Jens Axboe
2007-10-22 21:16 ` Benny Halevy
2007-10-22 21:21 ` Jeff Garzik
2007-10-22 21:47 ` Matt Mackall
2007-10-22 22:52 ` Alan Cox
2007-10-22 23:46 ` Matt Mackall
2007-10-23 0:11 ` Jeff Garzik
2007-10-23 4:09 ` powerpc: Fix fallout from sg_page() changes Olof Johansson
2007-10-23 4:31 ` IB/ehca: Fix sg_page() fallout Olof Johansson
2007-10-23 5:05 ` Jens Axboe
2007-10-23 5:54 ` Olof Johansson
2007-10-23 7:12 ` Jens Axboe
2007-10-23 7:13 ` powerpc: Fix fallout from sg_page() changes Jens Axboe
2007-10-23 17:08 ` [PATCH 09/10] Change table chaining layout Boaz Harrosh
2007-10-23 18:33 ` Jens Axboe
2007-10-23 19:56 ` Andi Kleen
2007-10-23 20:20 ` Jens Axboe
2007-10-23 20:57 ` Andi Kleen
2007-10-23 21:44 ` Jens Axboe
2007-10-22 18:11 ` [PATCH 10/10] Add CONFIG_DEBUG_SG sg validation Jens Axboe
2007-10-23 14:48 ` [PATCH][SG] fix typo in ps3rom.c Arnd Bergmann
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