Scheduler latency problems when using NAND

[Joakim Tjernlund]

>
> Mark Mason wrote:
> > Hi all,
> >
> > I hope this is the right place for this question.  I'm having some
> > problems with scheduler latency when using UBIFS, and I'm hoping for
> > some suggestions.
> <snip>
> > The application is storing streaming video, almost entirely large
> > sequential files, roughly 250K to 15M, to a 1.6G filesystem.  There's
> > no seeking or rewriting, just creat, write, close, repeat.  No
> > compression is used on the filesystem.
> >
> > The problem I'm seeing is excessively large scheduler latency when
> > data is flushed to NAND.
> <snip>
> > Does anyone have any suggestions, ideas, hints, advice, etc?
>
> The Linux block cache is optimised for mechanical hard drives,
> to minimise seek times. Some of the assumptions don't make much
> sense with FLASH and streaming storage.
>
> Maybe try to flush data whenever you have written a few blocks'
> worth. Or have a look at the O_DIRECT flag (or madvise), although
> I don't know how it interacts with UBIFS.
>
> Have you considered using a different file system? UBIFS is not
> exactly optimised for your use case. JFFS2 would be better, but
> won't stomach your flash size.

Perhaps try the new LogFS? Maybe it is better suited to this workload.

      Jocke