From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from main.gmane.org ([80.91.229.2] helo=ciao.gmane.org) by canuck.infradead.org with esmtps (Exim 4.52 #1 (Red Hat Linux)) id 1ELSGJ-000894-8S for linux-mtd@lists.infradead.org; Fri, 30 Sep 2005 17:17:57 -0400 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1ELSEo-0001yH-C6 for linux-mtd@lists.infradead.org; Fri, 30 Sep 2005 23:16:14 +0200 Received: from halhoupro3.halliburton.com ([64.154.26.251]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 30 Sep 2005 23:16:14 +0200 Received: from sergei.sharonov by halhoupro3.halliburton.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 30 Sep 2005 23:16:14 +0200 To: linux-mtd@lists.infradead.org From: Sergei Sharonov Date: Fri, 30 Sep 2005 21:15:53 +0000 (UTC) Message-ID: References: <433A640D.6030200@cetrtapot.si> <433BA402.3040703@inf.u-szeged.hu> <20050929093433.GB18741@wohnheim.fh-wedel.de> <433BB979.7010904@inf.u-szeged.hu> <433BBB19.9060905@yandex.ru> <1128010237.6926.10.camel@localhost.localdomain> <1128053984.6926.59.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: news Subject: Re: Great jffs2 speedup List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Peter, thanks for taking time to do the tests. > Hope that covers what you wanted to see. For the record, I am using the > head of mtd cvs with the centralized summary patch applied. EBS and CS > are both enabled. Aha!!! Of course, CS reduced your time to first write down to seconds. Could you repeat the test after the un-clean unmount (e.g. power off without sync)? I bet the numbers will be very different. Probably you also need to be writing to flash during the power off to force full scan on startup. > > Good point.. Can you estimate speedup due to the hw controller? > > We can get about 15 MB/s for raw reads and about 6 MB/s for raw writes. Hmm.. I was getting a read throughput jffs2 -> samba network fs of about 1.1 MB/s (180 MHz ARM9, linux 2.6.10, mtd 3/28/2005). I believe jffs2/mtd was the bottleneck since the throughput was 7.25x higher when files were comming from ext2/RAM. Looks like your hw controller is doing a good job. Not sure how overhead is split between mtd and jffs2. > By raw, I mean reading and writing via an mtd character device to/from a > raw partition. I do not know how these numbers compare to other flash > access methods; but bit-banging a flash part directly would have to be > considerably slower and probably very dependent on the CPU speed. My > device has a 384 MHz PowerPC 405 CPU, by the way. That helps too ;-) > > Most embedded systems cannot rely on proper shutdown. So, IMHO CS is of > > limited use in this respect. > > My device is usb powered, but has a small battery so that when the > device looses bus power, it can shutdown cleanly. Tricky, tricky, tricky ;-) Not everybody is that lucky to have a battery. Reminds me of a conversation with one "high reliability RTOS" vendor, you guess who. - Is your file system power fail safe? - Yes, of course. We do require that you use UPS though. > However, the thing to > remember about centralized summary is that in the unclean shutdown > cases, the mount time is no worse than jffs2 without CS. So even if you > only expect the filesystem to be cleanly unmounted sometimes, CS can be > worth it. As long as specification allows for an "occasional" 30 minutes startup time. Your hw controller does sound very interesting. What is the hardware implementation : asic, fpga? Is it available as a separate product (chip)? Sergei