linux-kernel - Re: [PATCH 7/7] sched, x86: Optimize the preempt

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Date:	Tue, 10 Sep 2013 16:25:17 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Mike Galbraith <bitbucket@...ine.de>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peter Anvin <hpa@...or.com>
Subject: Re: [PATCH 7/7] sched, x86: Optimize the preempt_schedule() call


* Jan Beulich <JBeulich@...e.com> wrote:

> >>> On 10.09.13 at 15:42, Ingo Molnar <mingo@...nel.org> wrote:
> 
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> >> +	.macro SAVE_ALL
> >> +	pushl_cfi %eax
> >> +	CFI_REL_OFFSET eax, 0
> >> +	pushl_cfi %ebp
> >> +	CFI_REL_OFFSET ebp, 0
> >> +	pushl_cfi %edi
> >> +	CFI_REL_OFFSET edi, 0
> >> +	pushl_cfi %esi
> >> +	CFI_REL_OFFSET esi, 0
> >> +	pushl_cfi %edx
> >> +	CFI_REL_OFFSET edx, 0
> >> +	pushl_cfi %ecx
> >> +	CFI_REL_OFFSET ecx, 0
> >> +	pushl_cfi %ebx
> >> +	CFI_REL_OFFSET ebx, 0
> >> +	.endm
> >> +
> >> +	.macro RESTORE_ALL
> >> +	popl_cfi %ebx
> >> +	CFI_RESTORE ebx
> >> +	popl_cfi %ecx
> >> +	CFI_RESTORE ecx
> >> +	popl_cfi %edx
> >> +	CFI_RESTORE edx
> >> +	popl_cfi %esi
> >> +	CFI_RESTORE esi
> >> +	popl_cfi %edi
> >> +	CFI_RESTORE edi
> >> +	popl_cfi %ebp
> >> +	CFI_RESTORE ebp
> >> +	popl_cfi %eax
> >> +	CFI_RESTORE eax
> >> +	.endm
> > 
> > Side note: shouldn't the pushl_cfi and popl_cfi macros be adjusted, 
> > instead of open coding it?
> 
> If you mean the open coding of CFI_REL_OFFSET and CFI_RESTORE, then no - 
> there may be pushes/pops that don't save the caller's register values 
> (i.e. where solely the frame pointer adjustment matters).

Ok.

> If you meant something else, please clarify what.

No, that's what I meant.

Thanks,

	Ingo
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