linux-kernel - Re: [PATCH v8 8/8] x86/tlb: do flush_tlb_kernel

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Message-ID: <20120613145656.GB32604@tassilo.jf.intel.com>
Date:	Wed, 13 Jun 2012 07:56:56 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Alex Shi <alex.shi@...el.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, arnd@...db.de,
	rostedt@...dmis.org, fweisbec@...il.com, jeremy@...p.org,
	seto.hidetoshi@...fujitsu.com, borislav.petkov@....com,
	tony.luck@...el.com, luto@....edu, riel@...hat.com, avi@...hat.com,
	len.brown@...el.com, tj@...nel.org, akpm@...ux-foundation.org,
	cl@...two.org, jbeulich@...e.com, eric.dumazet@...il.com,
	akinobu.mita@...il.com, cpw@....com, penberg@...nel.org,
	steiner@....com, viro@...iv.linux.org.uk,
	kamezawa.hiroyu@...fujitsu.com, aarcange@...hat.com,
	rientjes@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 8/8] x86/tlb: do flush_tlb_kernel_range by 'invlpg'

On Tue, Jun 12, 2012 at 05:06:45PM +0800, Alex Shi wrote:
> This patch do flush_tlb_kernel_range by 'invlpg'. The performance pay
> and gain was analyzed in my patch (x86/flush_tlb: try flush_tlb_single
> one by one in flush_tlb_range). Now we move this logical into kernel
> part. The pay is multiple 'invlpg' execution cost, that is same. but
>  the gain(cost reducing of TLB entries refilling) is absoulutely
> increased.

The subtle point is whether INVLPG flushes global pages or not.
After some digging I found a sentence in the SDM that says it does.
So it may be safe.

What does it improve?

-Andi
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