linux-kernel - Re: [PATCH v4 4/7] x86/tlb: fall back to flush all when meet a THP large page

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Date:	Thu, 10 May 2012 11:29:05 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Alex Shi <alex.shi@...el.com>
Cc:	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, arnd@...db.de, rostedt@...dmis.org,
	fweisbec@...il.com, jeremy@...p.org, gregkh@...uxfoundation.org,
	borislav.petkov@....com, riel@...hat.com, luto@....edu,
	avi@...hat.com, len.brown@...el.com, dhowells@...hat.com,
	fenghua.yu@...el.com, ak@...ux.intel.com, cpw@....com,
	steiner@....com, akpm@...ux-foundation.org, penberg@...nel.org,
	hughd@...gle.com, rientjes@...gle.com,
	kosaki.motohiro@...fujitsu.com, n-horiguchi@...jp.nec.com,
	paul.gortmaker@...driver.com, trenn@...e.de, tj@...nel.org,
	oleg@...hat.com, axboe@...nel.dk, kamezawa.hiroyu@...fujitsu.com,
	viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/7] x86/tlb: fall back to flush all when meet a THP
 large page

On Thu, 2012-05-10 at 13:00 +0800, Alex Shi wrote:
> We don't need to flush large pages by PAGE_SIZE step, that just waste
> time. and actually, large page don't need 'invlpg' optimizing according
> to our macro benchmark. So, just flush whole TLB is enough for them.
> 
> The following result is tested on a 2CPU * 4cores * 2HT NHM EP machine,
> with THP 'always' setting.

What does it do when you disable THP? That has_large_page() thing is a
massive amount of pointer chasing..
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