From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Eric Dumazet <dada1@cosmosbay.com>,
Rik van Riel <riel@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Ulrich Drepper <drepper@redhat.com>
Subject: Re: [PATCH] make MADV_FREE lazily free memory
Date: Thu, 12 Apr 2007 16:12:42 +1000 [thread overview]
Message-ID: <461DCDDA.2030502@yahoo.com.au> (raw)
In-Reply-To: <461DCCEB.70004@yahoo.com.au>
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.
WARNING: multiple messages have this Message-ID (diff)
From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Eric Dumazet <dada1@cosmosbay.com>,
Rik van Riel <riel@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Ulrich Drepper <drepper@redhat.com>
Subject: Re: [PATCH] make MADV_FREE lazily free memory
Date: Thu, 12 Apr 2007 16:12:42 +1000 [thread overview]
Message-ID: <461DCDDA.2030502@yahoo.com.au> (raw)
In-Reply-To: <461DCCEB.70004@yahoo.com.au>
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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next prev parent reply other threads:[~2007-04-12 6:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-11 4:30 [PATCH] make MADV_FREE lazily free memory Rik van Riel
2007-04-11 22:41 ` Eric Dumazet
2007-04-11 22:41 ` Eric Dumazet
2007-04-11 22:56 ` Rik van Riel
2007-04-11 22:56 ` Rik van Riel
2007-04-12 5:44 ` Eric Dumazet
2007-04-12 5:44 ` Eric Dumazet
2007-04-12 6:08 ` Nick Piggin
2007-04-12 6:08 ` Nick Piggin
2007-04-12 6:12 ` Nick Piggin [this message]
2007-04-12 6:12 ` Nick Piggin
2007-04-12 7:22 ` Rik van Riel
2007-04-12 7:22 ` Rik van Riel
2007-04-12 13:14 ` Nick Piggin
2007-04-12 13:14 ` Nick Piggin
2007-04-12 20:58 ` Rik van Riel
2007-04-13 0:34 ` Nick Piggin
2007-04-13 0:34 ` Nick Piggin
2007-04-16 16:10 ` Anton Blanchard
2007-04-16 16:10 ` Anton Blanchard
2007-04-16 16:30 ` Jakub Jelinek
2007-04-16 16:30 ` Jakub Jelinek
2007-04-16 18:39 ` Anton Blanchard
2007-04-16 18:39 ` Anton Blanchard
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