From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail1.danielind.com ([12.19.96.6]) by pentafluge.infradead.org with esmtp (Exim 3.22 #1 (Red Hat Linux)) id 14vKzp-0000wN-00 for ; Thu, 03 May 2001 16:26:26 +0100 Message-ID: <3AF178EB.89D9D094@daniel.com> Date: Thu, 03 May 2001 10:27:39 -0500 From: Vipin Malik MIME-Version: 1.0 To: David Woodhouse CC: mtd , jffs-dev Subject: Re: Wear Leveling in JFFS2 NOT working!(?) References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-mtd-admin@lists.infradead.org Errors-To: linux-mtd-admin@lists.infradead.org List-Help: List-Post: List-Subscribe: , List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: David Woodhouse wrote: > On Mon, 30 Apr 2001, Vipin Malik wrote: > > > Obviously, not all sectors are being "cycled" evenly. As a matter of > > fact, none of the sectors below 0x380000 are being cycled at all. > > > > Now, one thing that may be tripping up the wear leveling algorithm is > > the fact that the system is being cycled every 2-3 minutes. > > That's almost certainly the reason. My testing on prolonged stress tests > showed a fairly even wear levelling. Ok, I logged the current state of the num of sectors erased, stopped cycling power (but let the infinite write to JFFS2 continue). After 3 days I took another snapshot of the num erase sectors: (The results are posted below if anyone is interested) As hypothesized, the every few minutes cycling was what was screwing up the wear leveling algorithm. After the cycling stopped, all sectors showed up in the log and additionally each was cycled the same number of times! In my opinion, there should be no need to fix the algorithm to accommodate the frequent cycling. Power going down every few minutes is (usually) NOT a normal mode of operation of an embedded system. At least I'm happy with it the way it currently is. Vipin ************ Data follows ********************************************* ***Snap shot1 (when power was being cycled, you can see the uneven wear leveling of the sectors. Additionally only 20 sectors have ever been erased in >3000 cycles) **** Sector Address:0x780000 Number Of Erases:2823 Sector Address:0x640000 Number Of Erases:2162 Sector Address:0x600000 Number Of Erases:2077 Sector Address:0x5c0000 Number Of Erases:1939 Sector Address:0x580000 Number Of Erases:1795 Sector Address:0x500000 Number Of Erases:1454 Sector Address:0x4c0000 Number Of Erases:1146 Sector Address:0x7c0000 Number Of Erases:3143 Sector Address:0x740000 Number Of Erases:2627 Sector Address:0x700000 Number Of Erases:2499 Sector Address:0x6c0000 Number Of Erases:2410 Sector Address:0x680000 Number Of Erases:2280 Sector Address:0x540000 Number Of Erases:1644 Sector Address:0x480000 Number Of Erases:727 Sector Address:0x440000 Number Of Erases:301 Sector Address:0x400000 Number Of Erases:90 Sector Address:0x3c0000 Number Of Erases:17 Sector Address:0x380000 Number Of Erases:3 Total Unique Sectors Found= 20, total sum of all erases=29137 *** Power cycling was now stopped . Snapshot data follows (from after 1 days worth of writes to JFFS2) ********* Sector Address:0x780000 Number Of Erases:3214 Sector Address:0x640000 Number Of Erases:2552 Sector Address:0x600000 Number Of Erases:2467 Sector Address:0x5c0000 Number Of Erases:2330 Sector Address:0x580000 Number Of Erases:2185 Sector Address:0x500000 Number Of Erases:1844 Sector Address:0x4c0000 Number Of Erases:1537 Sector Address:0x7c0000 Number Of Erases:3534 Sector Address:0x740000 Number Of Erases:3018 Sector Address:0x700000 Number Of Erases:2889 Sector Address:0x6c0000 Number Of Erases:2800 Sector Address:0x680000 Number Of Erases:2670 Sector Address:0x540000 Number Of Erases:2035 Sector Address:0x480000 Number Of Erases:1118 Sector Address:0x440000 Number Of Erases:691 Sector Address:0x400000 Number Of Erases:480 Sector Address:0x3c0000 Number Of Erases:407 Sector Address:0x380000 Number Of Erases:393 Sector Address:0x340000 Number Of Erases:390 Sector Address:0x300000 Number Of Erases:390 Sector Address:0x2c0000 Number Of Erases:390 Sector Address:0x280000 Number Of Erases:390 Sector Address:0x240000 Number Of Erases:390 Sector Address:0x200000 Number Of Erases:390 Sector Address:0x1c0000 Number Of Erases:390 Sector Address:0x180000 Number Of Erases:390 Sector Address:0x140000 Number Of Erases:389 Sector Address:0x100000 Number Of Erases:389 Sector Address:0xc0000 Number Of Erases:389 Sector Address:0x80000 Number Of Erases:389 Sector Address:0x40000 Number Of Erases:389 Sector Address:0x0 Number Of Erases:389 Total Unique Sectors Found= 34, total sum of all erases=41618 ...and viola all sectors show up on the list and each has been erased *an additional* 389-390 times from the last snapshot when power cycling was still going on.