From manningc2@actrix.gen.nz Fri Feb 05 04:06:19 2010 Received: from smtp.firstline.co.nz ([203.167.210.162] helo=firstline.co.nz) by stoneboat.aleph1.co.uk with smtp (Exim 4.69) (envelope-from ) id 1NdFSQ-00038h-92 for yaffs@lists.aleph1.co.uk; Fri, 05 Feb 2010 04:06:19 +0000 Received: (qmail 30394 invoked by uid 453); 5 Feb 2010 04:06:02 -0000 X-Virus-Checked: Checked by ClamAV on firstline.co.nz Received: from Unknown (HELO linux-dual-head.local) (10.14.210.25) by firstline.co.nz (qpsmtpd/0.40) with ESMTP; Fri, 05 Feb 2010 17:06:02 +1300 From: Charles Manning To: yaffs@lists.aleph1.co.uk Date: Fri, 5 Feb 2010 17:05:55 +1300 User-Agent: KMail/1.9.10 References: <201002031315.15318.manningc2@actrix.gen.nz> <1E649C6B5AD2421E8F058091B48989A0@johanxp> In-Reply-To: <1E649C6B5AD2421E8F058091B48989A0@johanxp> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201002051705.56126.manningc2@actrix.gen.nz> X-SA-Exim-Connect-IP: 203.167.210.162 X-SA-Exim-Mail-From: manningc2@actrix.gen.nz X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on stoneboat.aleph1.co.uk X-Spam-Level: X-Spam-Status: No, score=-1.9 required=4.5 tests=AWL,BAYES_00,SPF_NEUTRAL autolearn=no version=3.2.5 X-SA-Exim-Version: 4.2.1 (built Wed, 25 Jun 2008 17:14:11 +0000) X-SA-Exim-Scanned: Yes (on stoneboat.aleph1.co.uk) Subject: Re: [Yaffs] multithreading question X-BeenThere: yaffs@lists.aleph1.co.uk X-Mailman-Version: 2.1.11 Precedence: list List-Id: Discussion of YAFFS NAND flash filesystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Feb 2010 04:06:20 -0000 On Wednesday 03 February 2010 23:17:42 Johan Kotlinski wrote: > Hi Charles! > > Thanks for your answer. Yes, I was talking about yaffs direct. Page-by-page > locking is of course all right. > > I have another question. Our NAND chip has the ability to prefetch pages. I > imagine we could benefit from this. Is there a way to get a hint from yaffs > what it is about to read next? Or do you know some good place to insert > such an optimization? > > Best regards, > Johan > I have just checked in code which breaks up long reads and writes into smaller sub read/writes. This has the advantage of reducing longing times. Please give this a whirl if it is of interest to you. -- Charles > ----- Original Message ----- > From: "Charles Manning" > To: > Cc: "Johan Kotlinski" > Sent: Wednesday, February 03, 2010 1:15 AM > Subject: Re: [Yaffs] multithreading question > > > On Tuesday 02 February 2010 00:29:17 Johan Kotlinski wrote: > >> Hi! > >> It appears that Yaffs2 multithreading protection is on a very high level > >> (mutex wrapping entire fread/fwrite calls). > > > > Are you talking about yaffs direct or the Linux yaffs? > > The linux yaffs will be locked on a page-by-page basis and I am going to > > change the way yaffs direct does the reading/writing too to only lock on > > a page-by-page basis. > > > > The underlying NAND is locked on a apge by page basis too (that's a > > limitation > > of the hardware), so is this really a big concern? > > > >> My worry is that if a low-priority task does a large fwrite call, it > >> could > >> block high-priority tasks for a long time. Is this an acknowledged > >> problem? > > > > It depends on the OS. Some, without priority inhere, won't have this > > problem. > > > >> Are there comparable file systems that handle multithreading in a more > >> granular way? > > _______________________________________________ > yaffs mailing list > yaffs@lists.aleph1.co.uk > http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs