JFFS2 Garbage collection issue

[Joakim Tjernlund]

"linux-mtd" <linux-mtd-bounces at lists.infradead.org> wrote on 2013/11/27 
11:23:25:
> 
> "linux-mtd" <linux-mtd-bounces at lists.infradead.org> wrote on 2013/11/27 
> 11:11:04:
> > 
> > Hi all,
> > 
> > we are currently facing a problem with the Garbage-collection on a 
JFFS2 
> 
> > file system.
> > 
> > We have an embedded linux system based on an ARM9 AT91RM9200 processor 

> > with an Intel / Micron JS28F256 NOR-flash of 32MB in size.
> > The Flash holds the U-Boot loader and its environment and in the main 
> > part (30MB) of the chip a JFFS2-based root-file-system.
> > Our Linux kernel version is 2.6.24.3
> > 
> > Some minutes after startup of the system, the garbage collector (gc.c) 

> > does a scan of the file system, gathering information for the garbage 
> > collection procedures that may be initiated based upon that data.
> > On some file systems, especially such with long runtime and therefore 
> > many file operations, this scan consumes a lot of time. On some 
systems 
> > it stays in that scan for more that 10 minutes. The problem with this 
> > behaviour is the fact, that during the scan the file system is locked, 

> > and therefore all file operations are suspended. This leads to a crash 

> > of the system, when the application program hangs for a long time, 
> > waiting for a file operation to return from a system call, and the 
> > watchdog is not triggered.
> > 
> > In a test system without watchdog, after the scan, the system runs 
> normally.
> > The flash chip itself shows no errors, so it seems to be a problem of 
> > the file system.
> > 
> > Any idea or suggestion to solve the problem would be very welcome!
> 
> The simple fix is to send a signal(SIGCONT?) to the GC process regularly 

> to do GC
> over time. That way you don't get all GC at boot time.
> 
>  Jocke

BTW, I guess you got logging to file such as syslog on your system?
JFFS2 really don't do well with small incremental writes. I recommend
you turn such logging off.