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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: dedekind1@gmail.com
Cc: "Hans J. Koch" <hjk@linutronix.de>,
	linux-mtd@lists.infradead.org,
	Adrian Hunter <adrian.hunter@nokia.com>
Subject: Re: ubifs: sync() causes writes even if nothing is changed
Date: Thu, 21 Oct 2010 10:23:01 +0200	[thread overview]
Message-ID: <4CBFF865.9010706@linutronix.de> (raw)
In-Reply-To: <1287581218.9272.67.camel@localhost>

Artem Bityutskiy wrote:
>> From a quick glance at the ubifs code, this might come out of the
>> garbage collector that is triggered on every sync() and writes
>> something even if nothing has changed.
>>
>> Is that really needed?
> 
> I briefly looked, and UBIFS is doing a lot of I/O in that case, which is
> unnecessary and should not be done, I'll need to investigate this.

 From what I've seen from the code there are two parts:
- writing "unwritten" data (the write back part I guess). Nothing is done
   here as long as no data is queued
- writing the journal. The first step seems to be to write a node "begin
   write" and the last one is "end write".

Since hjk sees only two erases I would guess that they are initiated by 
the "journal begin" & "end" requests.

Thanks for looking at this.

Sebastian

  reply	other threads:[~2010-10-21  8:23 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-10-13 16:30 ubifs: sync() causes writes even if nothing is changed Hans J. Koch
2010-10-15  6:13 ` Artem Bityutskiy
2010-10-20 13:26 ` Artem Bityutskiy
2010-10-21  8:23   ` Sebastian Andrzej Siewior [this message]
2010-10-21  8:32     ` Artem Bityutskiy
2010-10-21 17:04       ` Matthieu CASTET
2010-10-21 18:43         ` Artem Bityutskiy
2011-01-16 17:48 ` Artem Bityutskiy
2011-01-17  8:19   ` Adrian Hunter
2011-01-17  9:04     ` Artem Bityutskiy
2011-01-17 21:52     ` Artem Bityutskiy
2011-01-17 21:53     ` [PATCH v2 1/3] UBIFS: re-arrange variables in ubifs_info Artem Bityutskiy
2011-01-17 21:54       ` [PATCH v2 2/3] UBIFS: introduce mounting flag Artem Bityutskiy
2011-01-18  7:30     ` [PATCH v2 3/3] UBIFS: do not start the commit if there is nothing to commit Artem Bityutskiy
2011-01-18  7:36       ` Artem Bityutskiy
2011-01-18 12:29         ` John Ogness
2011-01-21 11:13           ` Artem Bityutskiy
2011-01-21 11:28             ` John Ogness
2011-01-25  8:20               ` Artem Bityutskiy

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