JFFS2 access time

Hi all,

We are using uClinux git 2.6.23. We have 4 2.5MB files sitting in a directory on a ~40MB jffs2 partition (on NOR flash). The very first time we do an 'ls' in that directory, the response takes literally minutes. After the initial delay, any accesses to those files are very quick.,,Originally, we started off with the Microtronix 1.4 kernel and it did not have this problem. The pre-git version of uClinux-dist had this problem but not as severe - it was more like 40 seconds to list the contents of that directory.

Thanks in advance,

By "the first time" to you mean the first time you boot the board at all, or the first time after each boot?

If you download a 10 MB JFFS2 image into a 40 MB partition, then JFFS2 will upon mounting erase each flash sector in the unused 30 MB area and write cleanmarkers to it. This more or less blocks accesses to the flash during this time. However, this only occurs the first time the system is booted, after that, the partition is completely "JFFS2-formatted" and there shouldn't be any further delays.

/Ricard

That is normal for large files. JFFS2 has do the CRC checking on all the nodes for those large files. That is a lot of nodes to check. You might want to look into using the eraseblock summary feature.

I have no idea what those two kernels are, but older JFFS2 used to do all the CRC checking at mount time. So mount would be slow and runtime access would be relatively quick.

josh

The Microtronix kernel is the kernel built by Altera's Quartus 6.1 suite. By "pre-git" version, we just meant the packaged version from nioswiki, rather than getting it from the git server.

At any rate, it turns out that having the verbosity level set to 2 in the jffs2 section of menuconfig was our problem. The kernel was so dragged down by having to bombard /proc/kmsg with jffs2 printk's that it caused the huge delays we were seeing. We set verbosity back to 0 and all is well.

Thanks :-)