linux-kernel - Re: x86: Is there still value in having a special tlb flush IPI vector?

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Date:	Thu, 31 Jul 2008 22:57:26 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Jens Axboe <jens.axboe@...cle.com>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: x86: Is there still value in having a special tlb flush IPI
	vector?


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Peter Zijlstra wrote:
> > How about using just arch_send_call_function_single_ipi() to implement
> > smp_send_reschedule() ?
> >
> > The overhead of that is a smp_mb() and a list_empty() check in
> > generic_smp_call_function_single_interrupt() if there is indeed no work
> > to do.
> 
> Is doing a no-op interrupt sufficient on all architectures?  Is there 
> some change a function call IPI might not go through the normal 
> reschedule interrupt exit path?

We'd still use the smp_send_reschdule(cpu) API, so it's an architecture 
detail. On x86 we'd use arch_send_call_function_single_ipi().

	Ingo
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