linux-kernel - Re: [PATCH 2/3] x86: mm: Change tlb_flushall

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Date:	Fri, 13 Dec 2013 10:11:05 +0800
From:	Alex Shi <alex.shi@...aro.org>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Mel Gorman <mgorman@...e.de>, H Peter Anvin <hpa@...or.com>,
	Linux-X86 <x86@...nel.org>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH 2/3] x86: mm: Change tlb_flushall_shift for IvyBridge

On 12/13/2013 09:02 AM, Alex Shi wrote:
>> > You have not replied to this concern of mine: if my concern is valid 
>> > then that invalidates much of the current tunings.
> The benefit from pretend flush range is not unconditional, since invlpg
> also cost time. And different CPU has different invlpg/flush_all
> execution time. 

TLB refill time is also different on different kind of cpu.

BTW,
A bewitching idea is till attracting me.
https://lkml.org/lkml/2012/5/23/148
Even it was sentenced to death by HPA.
https://lkml.org/lkml/2012/5/24/143

That is that just flush one of thread TLB is enough for SMT/HT, seems
TLB is still shared in core on Intel CPU. This benefit is unconditional,
and if my memory right, Kbuild testing can improve about 1~2% in average
level.

So could you like to accept some ugly quirks to do this lazy TLB flush
on known working CPU?
Forgive me if it's stupid.

-- 
Thanks
    Alex
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