NAND out of space crash

[Jim Gettys]

There are two issues here that we should be sure to not intertwingle:

1) whatever behavior Sugar may have when low/out of space, during
operation, or at boot time.

2) JFFS2's behavior when the file system is almost full.  When it gets
almost full, it can spend all its time trying to garbage collect, and
you can lose completely (the system sort of gets the "slows", and grinds
to a halt).

As to 2), there are patches done by Nokia (deployed on the N800 and
similar devices) that reserve some extra space and report out of space
before the system "gets the slows".  These are in Dave's incoming queue
to merge into JFFS2 the last I heard.  I don't know if he's merged them.
                        - Jim




On Mon, 2008-07-21 at 13:45 -0300, John Watlington wrote:
> I think this is a huge problem.   Here in Uruguay they are seeing
> a flood of machines with this problem, and it will only get worse
> over time (and we will encounter this in every other deployment
> soon.)
> 
> They desperately need a fix...
> 
> wad
> 
> On Jul 21, 2008, at 12:55 PM, Greg Smith wrote:
> 
> > Hi All,
> >
> > I found http://dev.laptop.org/ticket/7125 which looks like a good  
> > place
> > to track this problem.
> >
> > I marked it blocker for 8.2.0.
> >
> > Here's what I think we need:
> > - Sugar GUI always starts, no matter how much space is free on the  
> > NAND.
> > - If Sugar starts and you are low on space (exact size tbd) then we
> > should alert the user to start clearing space in the journal.
> >
> > I think Eben will work on the second part. Can someone solve the first
> > part?
> >
> > Suggested steps would be to propose a solution, get buy in, code it  
> > and
> > check it in.
> >
> > I shouldn't have mentioned partitioning :-( All I meant was that we
> > cannot solve this on upgrade by whacking all user data.
> >
> > Thanks,
> >
> > Greg S
> >
> >> Date: Sat, 19 Jul 2008 12:39:04 -0400
> >> From: Erik Garrison <erik at laptop.org>
> >> Subject: Re: NAND out of space crash (was Display warnings in sugar
> >> 	(Emiliano Pastorino))
> >> To: greg at laptop.org
> >> Cc: devel at lists.laptop.org
> >> Message-ID: <20080719163904.GS9041 at eggs>
> >> Content-Type: text/plain; charset=us-ascii
> >>
> >> On Sat, Jul 19, 2008 at 11:47:21AM -0400, Greg Smith wrote:
> >>> Hi All,
> >>>
> >>> Emiliano has an elegant workaround but crashing the XO on NAND  
> >>> full (to
> >>> un-recoverable state?) is a heinous bug that affects essentially  
> >>> all users.
> >>>
> >>> If someone has the bug ID handy can you send it out and mark it a
> >>> blocker for 8.2.0 (priority = blocker and keyword includes blocks: 
> >>> 8.2.0)?
> >>>
> >>> Can I get a design proposal (no re-partitioning please!), scoping  
> >>> and
> >>> lead engineer on it ASAP?
> >>>
> >>> If you have to stop working on something else to do this, let me  
> >>> know
> >>> what will drop and I'll help weigh the consequences.
> >>
> >> My impression is that the long-term benefits of partitioning mean  
> >> that
> >> it's worthwhile to devote effort to it.  Are we not going to work on
> >> partitioning in the future?
> >>
> >> In addition to a more solid solution to the NAND fillup issue, we get
> >> the opportunity to improve system performance and upgrade procedures.
> >> Partitioning will allow us to test out LZO data compression for  
> >> the XO's
> >> filesystems (excluding /boot and /security).  We would expect a
> >> significant i/o performance boost from the use of LZO.  Additionally,
> >> partitioning would improve OFW-level system updates (e.g. copy- 
> >> nand) by
> >> making it far simpler for the update procedure to leave user data
> >> intact.
> >>
> >> That said there are obviously a lot of troubles with partitioning.
> >> Updating an existing system to a partitioned one without mashing user
> >> data is a major issue.
> >>
> >> Erik
> >>
> >>
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> 
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-- 
Jim Gettys <jg at laptop.org>
One Laptop Per Child