From mboxrd@z Thu Jan 1 00:00:00 1970 From: Detlev Zundel Date: Wed, 27 Apr 2011 11:43:42 +0200 Subject: [U-Boot] [PATCH,V2] JFFS2: accelerate scanning. In-Reply-To: (Baidu Liu's message of "Sun, 24 Apr 2011 11:43:37 +0800") References: <000001cbfcbd$59578ec0$6401a8c0@LENOVOE5CA6843> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Baidu, > Hi,Detlev : > > 2011/4/19 Detlev Zundel : >> Hi Baidu, >> >>> ?Syncs up with jffs2 in the linux kernel: >>> ?1/ Change DEFAULT_EMPTY_SCAN_SIZE from 4KB to 256 Bytes. >>> ?2/ If the 1KB data is 0xFF after the cleanmarker, skip >>> ?and scan the next sector. >>> ?3/ Change the buffer size from 4KB to 128KB which is the >>> ?common size of erase block. >> >> There is no "common size of erase block". ?Looking into the Linux code, >> it uses "max(erase block size, 128k)" for its buffer to speed up reading >> from NAND and the 128k seem to be a kmalloc limit. >> >> So maybe a "increase buffer size from 4KiB to 128KiB to reduce number of >> read operations" would be more fitting. ?By the way, does this change >> contribute to the performance increase at all, or is the increase simply >> due to DEFAULT_EMPTY_SCAN_SIZE? >> > > Yes, I think it is useful to speed up the scanning. Don't get me wrong, but I was not asking whether you "think" it speeds up the scanning. When it comes to performance, I learnt to trust numbers olnly. This may in part be because I myself occassionally was completely wrong in predicting performance issues. So I am still eager to see actual numbers if this _really_ speeds up scanning. Cheers Detlev -- Die meisten schaetzen nicht, was sie verstehen; aber was sie nicht fassen koennen, verehren sie. Um geschaetzt zu werden, muessen die Sachen Muehe kosten; daher wird geruehmt, wer nicht verstanden wird. --- Baltasar Gracian -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de