linux-kernel - Re: [RFC][PATCH 0/6] Another go at speculative page faults

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Message-ID: <5448DB05.5050803@cn.fujitsu.com>
Date:	Thu, 23 Oct 2014 18:40:05 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	"Kirill A. Shutemov" <kirill@...temov.name>,
	Ingo Molnar <mingo@...nel.org>,
	<torvalds@...ux-foundation.org>, <paulmck@...ux.vnet.ibm.com>,
	<tglx@...utronix.de>, <akpm@...ux-foundation.org>,
	<riel@...hat.com>, <mgorman@...e.de>, <oleg@...hat.com>,
	<mingo@...hat.com>, <minchan@...nel.org>,
	<kamezawa.hiroyu@...fujitsu.com>, <viro@...iv.linux.org.uk>,
	<dave@...olabs.net>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>
Subject: Re: [RFC][PATCH 0/6] Another go at speculative page faults

On 10/22/2014 01:56 AM, Peter Zijlstra wrote:
> On Tue, Oct 21, 2014 at 08:09:48PM +0300, Kirill A. Shutemov wrote:
>> It would be interesting to see if the patchset affects non-condended case.
>> Like a one-threaded workload.
> 
> It does, and not in a good way, I'll have to look at that... :/

Maybe it is blamed to find_vma_srcu() that it doesn't take the advantage of
the vmacache_find() and cause more cache-misses.


Is it hard to use the vmacache in the find_vma_srcu()?

> 
>  Performance counter stats for './multi-fault 1' (5 runs):
> 
>         73,860,251      page-faults                                                   ( +-  0.28% )
>             40,914      cache-misses                                                  ( +- 41.26% )
> 
>       60.001484913 seconds time elapsed                                          ( +-  0.00% )
> 
> 
>  Performance counter stats for './multi-fault 1' (5 runs):
> 
>         70,700,838      page-faults                                                   ( +-  0.03% )
>             31,466      cache-misses                                                  ( +-  8.62% )
> 
>       60.001753906 seconds time elapsed                                          ( +-  0.00% )
> .
> 

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