linux-kernel - Re: [PATCH 3/3] [RFC] tmpfs: Add FALLOC_FL_MARK_VOLATILE/UNMARK

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Message-ID: <4FD63A55.3090505@linaro.org>
Date:	Mon, 11 Jun 2012 11:35:01 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Rik van Riel <riel@...hat.com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
	Hugh Dickins <hughd@...gle.com>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Andrea Righi <andrea@...terlinux.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Taras Glek <tgek@...illa.com>, Mike Hommey <mh@...ndium.org>,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 3/3] [RFC] tmpfs: Add FALLOC_FL_MARK_VOLATILE/UNMARK_VOLATILE
 handlers

On 06/10/2012 02:47 PM, Rik van Riel wrote:
> On 06/08/2012 11:45 PM, John Stultz wrote:
>
>> I *think* ideally, the pages in a volatile range should be similar to
>> non-dirty file-backed pages. There is a cost to restore them, but
>> freeing them is very cheap. The trick is that volatile ranges introduces
>
> Easier to mark them dirty.
>
>> a new relationship between pages. Since the neighboring virtual pages in
>> a volatile range are in effect tied together, purging one effectively
>> ruins the value of keeping the others, regardless of which zone they are
>> physically.
>
> Then the volatile ->writepage function can zap the whole
> object.
>

What about the concern that if we don't have swap, we'll not call 
writepage on tmpfs files?

thanks
-john





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