linux-kernel - Re: [RFC][PATCH 6/8] mm: handle_speculative

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Message-ID: <4B496546.5010607@vflare.org>
Date:	Sun, 10 Jan 2010 10:57:34 +0530
From:	Nitin Gupta <ngupta@...are.org>
To:	Ed Tomlinson <edt@....ca>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, cl@...ux-foundation.org,
	"hugh.dickins" <hugh.dickins@...cali.co.uk>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()

On 01/09/2010 08:17 PM, Ed Tomlinson wrote:
> On Friday 08 January 2010 11:53:30 Peter Zijlstra wrote:
>> On Tue, 2010-01-05 at 20:20 -0800, Linus Torvalds wrote:
>>>
>>> On Wed, 6 Jan 2010, KAMEZAWA Hiroyuki wrote:
>>>>>
>>>>> Of course, your other load with MADV_DONTNEED seems to be horrible, and 
>>>>> has some nasty spinlock issues, but that looks like a separate deal (I 
>>>>> assume that load is just very hard on the pgtable lock).
>>>>
>>>> It's zone->lock, I guess. My test program avoids pgtable lock problem.
>>>
>>> Yeah, I should have looked more at your callchain. That's nasty. Much 
>>> worse than the per-mm lock. I thought the page buffering would avoid the 
>>> zone lock becoming a huge problem, but clearly not in this case.
>>
>> Right, so I ran some numbers on a multi-socket (2) machine as well:
>>
>>                                pf/min
>>
>> -tip                          56398626
>> -tip + xadd                  174753190
>> -tip + speculative           189274319
>> -tip + xadd + speculative    200174641
> 
> Has anyone tried these patches with ramzswap?  Nitin do they help with the locking
> issues you mentioned?
> 

Locking problem with ramzswap seems completely unrelated to what is being discussed here.

Thanks,
Nitin
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