linux-kernel - Re: [PATCH 1/6] x86, 32-bit: Add new pt

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Date:	Wed, 09 Dec 2009 16:05:28 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Brian Gerst <brgerst@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, x86@...nel.org,
	torvalds@...ux-foundation.org, jeremy@...p.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] x86, 32-bit: Add new pt_regs stubs

On 12/09/2009 04:01 PM, Brian Gerst wrote:
> Add new stubs which add the pt_regs pointer as the last arg, matching
> 64-bit.  This will allow these syscalls to be easily merged.
> 
> Signed-off-by: Brian Gerst <brgerst@...il.com>
> +ptregs_##name: \
> +	leal 4(%esp),%edx; \
> +	movl PT_EBX(%edx),%eax; \
> +	jmp sys_##name;

You're introducing a completely unnecessary pipeline serialization here.
 Instead do:

	movl (PT_EBX+4)(%esp),%eax;

... making the statements independent and therefore executable in parallel.

	-hpa
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