linux-kernel - Re: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of siblings of SMT

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Message-ID: <4FBDC34E.5090905@intel.com>
Date:	Thu, 24 May 2012 13:12:46 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Andrew Lutomirski <luto@....edu>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Jan Beulich <JBeulich@...e.com>, borislav.petkov@....com,
	arnd@...db.de, akinobu.mita@...il.com, eric.dumazet@...il.com,
	fweisbec@...il.com, rostedt@...dmis.org, hughd@...gle.com,
	jeremy@...p.org, len.brown@...el.com, tony.luck@...el.com,
	yongjie.ren@...el.com, kamezawa.hiroyu@...fujitsu.com,
	seto.hidetoshi@...fujitsu.com, penberg@...nel.org,
	yinghai@...nel.org, tglx@...utronix.de, akpm@...ux-foundation.org,
	ak@...ux.intel.com, avi@...hat.com, dhowells@...hat.com,
	mingo@...hat.com, riel@...hat.com, cpw@....com, steiner@....com,
	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	hpa@...or.com
Subject: Re: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of siblings
 of SMT

On 05/24/2012 09:46 AM, Andrew Lutomirski wrote:

> On Wed, May 23, 2012 at 10:15 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>> On Wed, 2012-05-23 at 19:09 +0200, Peter Zijlstra wrote:
>>>> There is no comment or anything else indicating that this is
>>>> suitable for dual-thread CPUs only - when there are more than
>>>> 2 threads per core, the intended effect won't be achieved.
>>>
>>> Why would that be? Won't higher thread count still share the same
>>> resources just more so?
>>
>> Ah, I see, you're saying his code is buggy for >2 threads. Agreed.
>>
> 
> An evil knob to statically choose which SMT sibling gets the interrupt
> would be nice.  Then my compute-intensive thread could be (mostly)
> unaffected by the other thread on a different core that calls munmap
> frequently.


How to know we are in such situation? :)

> 
> --Andy


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