Re: [ECOS] JFFS2 eats memory

[Øyvind Harboe <oyvind dot harboe at zylin dot com>]

On Tue, 2004-07-13 at 12:05, David Woodhouse wrote:
> On Tue, 2004-07-13 at 11:49 +0200, Øyvind Harboe wrote:
> > Changing the size of jffs2_raw_node_ref does not help much, since the
> > problem is that my system runs out of memory since it continously
> > overwrites existing files, thus filling up the flash with obsoleted
> > nodes.
> 
> It'll help in a lot of cases. You have a jffs2_raw_node_ref for _all_
> data nodes which are physically present on the flash, whether the inodes
> to which they belong are opened or not. There can be thousands of these.
> 
> In Linux we also use a different allocator, allocating these from
> fixed-size slabs so there isn't an 8-byte overhead for each one. 

When I say that reducing size does not "help", I mean that the problem
with memory usage constantly increasing persits. It just takes a bit
longer, e.g. my system falls over in 4 days instead of 1, which in my
case makes no difference.

> 
> > I'm pretty sure the problem is in the file fragment list...
> 
> What's the problem?

I'd like to take this oportunity to say that I'm trying to address this
problem because I need to, not because my eCos/JFFS2 knowledge is up to
the task. 

>  You say the problem goes away when you prune the
> icache...

My problem *almost* goes away with the icache_evict() change.

>  that implies that there's nothing being _lost_, but you're
> just objecting to the fact that your inode cache is doing any caching.
> 
> It's keeping the inode around for you in case you open it again
> immediately, because it _knows_ the garbage collector tends to exhibit
> that kind of behaviour. You made it stop doing that, and your problem
> went away, right?

No, it almost went away. 24 bytes is still lost every time I
overwrite/delete a file

> Can you join #mtd on irc.freenode.net?

I took it for a quick spin, but got some error messages. Perhaps some
firewall issues, etc. I'm not familiar with IRC.

> > Thats a lot more than I want to attempt with my current knowledge about
> > JFFS2. :-)
> 
> It's not about JFFS2. It's about eCos. The complex parts of the JFFS2
> bits are in the core JFFS2 code which you're not expected to touch. IT's
> the eCos wrapper around that core code which needs a rewrite :)

I see.

-- 
Øyvind Harboe
http://www.zylin.com



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