linux-kernel - Re: [PATCH 0 of 8] x86/smp function calls: convert x86 tlb flushes to use function calls

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Date:	Wed, 6 Aug 2008 05:37:36 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 0 of 8] x86/smp function calls: convert x86 tlb flushes to use function calls

On Tue, Aug 05, 2008 at 08:33:24PM -0700, Jeremy Fitzhardinge wrote:
> Andi Kleen wrote:
> >Jeremy Fitzhardinge <jeremy@...p.org> writes:
> >
> >  
> >>1. use smp_call_function_mask to implement cross-cpu TLB flushes
> >>    
> >
> >
> >Do you have any measurements comparing performance of the old and 
> >the new call? TLB flush is quite time critical so we should be very
> >careful here.
> 
> No.  What benchmark would you suggest?

Micro benchmark. Just stick RDTSC around the calls and trigger
a few remote flushes by e.g. doing mmap/munmap on a multithreaded program
running on different CPUs.

-Andi
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