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From: Andrew Morton <>
To: David Miller <>
Subject: Re: Size of 2.6.20 task_struct on x86_64 machines
Date: Thu, 8 Feb 2007 13:03:00 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 08 Feb 2007 12:19:45 -0800 (PST)
David Miller <> wrote:

> From: William Cohen <>
> Date: Thu, 08 Feb 2007 11:14:13 -0500
> > This past week I was playing around with that pahole tool
> > ( and looking at the
> > size of various struct in the kernel. I was surprised by the size of
> > the task_struct on x86_64, approaching 4K.  I looked through the
> > fields in task_struct and found that a number of them were declared as
> > "unsigned long" rather than "unsigned int" despite them appearing okay
> > as 32-bit sized fields. On x86_64 "unsigned long" ends up being 8
> > bytes in size and forces 8 byte alignment. Is there a reason there
> > a reason they are "unsigned long"?
> I think at one point we used the atomic bit operations to operate on
> things like tsk->flags, and those interfaces require unsigned long as
> the type.
> That doesn't appear to be the case any longer, so at a minimum
> your tsk->flags conversion to unsigned int should be ok.

Yeah, afacit everything in there is OK and happily all the
converted-to-32-bit quantities happen to be contiguous with other 32-bit

Most architectures' bitops functions take unsigned long * so if anyone is
using bitops on these things we should get to hear about it.

  reply	other threads:[~2007-02-08 21:03 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-08 16:14 William Cohen
2007-02-08 20:19 ` David Miller
2007-02-08 21:03   ` Andrew Morton [this message]
2007-02-11  0:20 ` Dave Jones
2007-02-11  2:55   ` Linus Torvalds

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