linux-kernel - Re: [PATCH] make MADV

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Date:	Thu, 12 Apr 2007 16:12:42 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Nick Piggin <nickpiggin@...oo.com.au>
CC:	Eric Dumazet <dada1@...mosbay.com>, Rik van Riel <riel@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: [PATCH] make MADV_FREE lazily free memory

Nick Piggin wrote:
> Eric Dumazet wrote:
> 

>>> Two things can happen here.
>>>
>>> If this program used the pages before the kernel needed
>>> them, the program will be reusing its old pages.
>>
>>
>>
>> ah ok, this is because accessed/dirty bits are set by hardware and not 
>> a page fault.
> 
> 
> No it isn't.

That is to say, it isn't required for correctness. But if the
question was about avoiding a fault, then yes ;)

But as Linus recently said, even hardware handled faults still
take expensive microarchitectural traps.

> 
>> Is it true for all architectures ?
> 
> 
> No.
> 


-- 
SUSE Labs, Novell Inc.
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