linux-ext4 - Re: [PATCH 0/2] new API to allocate buffer-cache for superblock in non-movable area

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Message-ID: <53E1C7F5.7040901@lge.com>
Date:	Wed, 06 Aug 2014 15:15:17 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>
CC:	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, linux-mm@...ck.org,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH 0/2] new API to allocate buffer-cache for superblock in
 non-movable area



2014-08-02 오전 1:04, Peter Zijlstra 쓴 글:
> On Fri, Aug 01, 2014 at 05:24:59PM +0200, Jan Kara wrote:
>
>>    OK, makes sense. But then if there's heavy IO going on, anything that has
>> IO pending on it is pinned and IO completion can easily take something
>> close to a second or more. So meeting subsecond deadlines may be tough even
>> for ordinary data pages under heavy load, even more so for metadata where
>> there are further constraints. OTOH phones aren't usually IO bound so in
>> practice it needn't be so bad ;).
>
> Yeah, typically phones are not IO bound :-)
>
>> So if it is sub-second unless someone
>> loads the storage, then that sounds doable even for metadata. But we'll
>> need to attach ->migratepage callback to blkdev pages and at least in ext4
>> case teach it how to move pages tracked by the journal.
>
> Right, making it possible at all if of course much prefered over not
> possible, regardless of timeliness :-)
>
>>> Sadly its not only mobile devices that excel in crappy hardware, there's
>>> plenty desktop stuff that could use this too, like some of the v4l
>>> devices iirc.
>>    Yeah, but in such usecases the guarantees we can offer for completion of
>> migration are even more vague :(.
>
> Yeah, lets start by making it possible, after that we can maybe look at
> making it better, who knows.
>

Is my patch applicable? Or what do I have to do now?
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