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From: David Woodhouse <dwmw2@infradead.org>
To: Jasmine Strong <jasmine@hex.linuxgrrls.org>
Cc: John Hall <John.Hall@optionexist.co.uk>,
	"Linux MTD list (E-mail)" <linux-mtd@lists.infradead.org>
Subject: Re: Stable cvs version for 2.4
Date: Wed, 04 Sep 2002 15:37:00 +0100	[thread overview]
Message-ID: <547.1031150220@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0209041519170.22265-100000@hex.linuxgrrls.org>

jasmine@hex.linuxgrrls.org said:
>  Yes.  uCLinux, anyway.   Pointers should always be treated as opaque
> unless you have a *really* good reason not to.

I have 8000 reasons not to:

# grep node_frag /proc/slabinfo 
jffs2_node_frag     8028   8064     28   64   64    1

At a gratuitous extra 4 bytes per object, that's... ok, well it's only
wasting 32KiB which is less than I expected, but it still annoys me.

> (Architectures that don't always use word-aligned pointers include
> m68k and ARM Thumb.) 

Even when we're allocating from the slab and the object in question is a 
structure of size which is an even number?

Even so, I'd assume that we care even _more_ about that 32KiB on uCLinux, so
maybe it's worth adding 1 byte of padding to the structure there and
manually aligning the pointer after allocating, or something. We only need 
1 bit, after all. Or we could use the _top_ bit on uCLinux, perhaps?

--
dwmw2

  reply	other threads:[~2002-09-04 14:38 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-03 10:09 Stable cvs version for 2.4 John Hall
2002-09-03 12:29 ` David Woodhouse
2002-09-04  0:18   ` David Woodhouse
2002-09-04  1:14     ` Jasmine Strong
2002-09-04  8:51       ` David Woodhouse
2002-09-04 14:21         ` Jasmine Strong
2002-09-04 14:37           ` David Woodhouse [this message]
2002-09-04 14:46             ` Allen Curtis
2002-09-04 14:54               ` Jasmine Strong
2002-09-04 15:17                 ` Steve Wahl
2002-09-04 15:26                   ` David Woodhouse
2002-09-04 15:20                 ` David Woodhouse
2002-09-04 15:33                   ` Jasmine Strong
2002-09-04 15:44                     ` David Woodhouse
2002-09-04 15:50                     ` Allen Curtis
2002-09-04 15:54                       ` David Woodhouse
2002-09-04 14:49             ` Jasmine Strong
2002-09-04 15:06               ` David Woodhouse

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