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

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Message-ID: <28c262361001042224u44bad2e8r8eafdbdff673076a@mail.gmail.com>
Date:	Tue, 5 Jan 2010 15:24:45 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"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 Tue, Jan 5, 2010 at 3:09 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> On Tue, 5 Jan 2010 15:09:47 +0900
> Minchan Kim <minchan.kim@...il.com> wrote:
>> My humble opinion is following as.
>>
>> Couldn't we synchronize rcu in that cases(munmap, exit and so on)?
>> It can delay munap and exit but it would be better than handling them by more
>> complicated things, I think. And both cases aren't often cases so we
>> can achieve advantage than disadvantage?
>>
>
> In most case, a program is single threaded. And sychronize_rcu() in unmap path
> just adds very big overhead.

Yes.
I suggested you that consider single-thread app's regression, please. :)

First I come to my head is we can count number of thread.
Yes. thread number is a not good choice.

As a matter of fact, I want to work it adaptively.
If the process start to have many threads, speculative page fault turn
on or turn off.
I know it's not easy. I hope other guys have good ideas.

>
> Thanks,
> -Kame
>
>



-- 
Kind regards,
Minchan Kim
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