linux-kernel - Re: [PATCH 3/3] smp.h: Move !SMP version of on_each

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Message-ID: <51FC31AF.1070802@caviumnetworks.com>
Date:	Fri, 2 Aug 2013 15:24:47 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>
CC:	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 3/3] smp.h: Move !SMP version of on_each_cpu() out-of-line

On 08/02/2013 02:09 PM, David Daney wrote:
> From: David Daney <david.daney@...ium.com>
>
> All of the other non-trivial !SMP versions of functions in smp.h are
>  out-of-line in up.c.  Move on_each_cpu() there as well.
>
> This allows us to get rid of the #include <linux/irqflags.h>.  The
> drawback is that this makes both the x86_64 and i386 defconfig !SMP
> kernels about 200 bytes larger each.

I looked at the cause of the size difference and there are several main
parts to it.

1) kallsym data (28 bytes).

2) with the patch generating a function pointer to pass to on_each_cpu 
vs. direct call (7 bytes * 22 call sites) and generating the the ignored 
third parameter (5 bytes * 22 call sites); without the patch 
local_irq_save/local_irq_restore(5 bytes * 22 call sites)  for a total 
of 7 * 22 == 154 bytes.

3) Other (21 bytes).

>
> Signed-off-by: David Daney <david.daney@...ium.com> ---
> include/linux/smp.h | 21 +++++---------------- kernel/up.c         |
> 11 +++++++++++ 2 files changed, 16 insertions(+), 16 deletions(-)
>

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