From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <djwong@us.ibm.com>, Theodore Tso <tytso@mit.edu>,
        Alexander Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Jeff Layton <jlayton@redhat.com>, Dave Chinner <david@fromorbit.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Christoph Hellwig <hch@infradead.org>, linux-mm@kvack.org,
        Chris Mason <chris.mason@oracle.com>, Joel Becker <jlbec@evilplan.org>,
        linux-scsi <linux-scsi@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-ext4@vger.kernel.org, Mingming Cao <mcao@us.ibm.com>
Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses
References: <20110509230318.19566.66202.stgit@elm3c44.beaverton.ibm.com>
	<87tyd31fkc.fsf@devron.myhome.or.jp>
	<20110510123819.GB4402@quack.suse.cz>
	<87hb924s2x.fsf@devron.myhome.or.jp>
	<20110510132953.GE4402@quack.suse.cz>
	<878vue4qjb.fsf@devron.myhome.or.jp>
	<87zkmu3b2i.fsf@devron.myhome.or.jp>
	<20110510145421.GJ4402@quack.suse.cz>
Date: Wed, 11 May 2011 01:12:13 +0900
In-Reply-To: <20110510145421.GJ4402@quack.suse.cz> (Jan Kara's message of
	"Tue, 10 May 2011 16:54:21 +0200")
Message-ID: <87zkmupmaq.fsf@devron.myhome.or.jp>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 907
Lines: 22

Jan Kara <jack@suse.cz> writes:

>> Did you already consider, to copy only if page was writeback (like
>> copy-on-write)? I.e. if page is on I/O, copy, then switch the page for
>> writing new data.
>   Yes, that was considered as well. We'd have to essentially migrate the
> page that is under writeback and should be written to. You are going to pay
> the cost of page allocation, copy, increased memory & cache pressure.
> Depending on your backing storage and workload this may or may not be better
> than waiting for IO...

Maybe possible, but you really think on usual case just blocking is
better?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/