Re: [Yaffs] multithreading question

On Wednesday 03 February 2010 23:17:42 Johan Kotlinski wrote:
> Hi Charles!
>
> Thanks for your answer. Yes, I was talking about yaffs direct. Page-by-page
> locking is of course all right.
>
> I have another question. Our NAND chip has the ability to prefetch pages. I
> imagine we could benefit from this. Is there a way to get a hint from yaffs
> what it is about to read next? Or do you know some good place to insert
> such an optimization?
>
> Best regards,
> Johan
>
I have just checked in code which breaks up long reads and writes into smaller
sub read/writes.

This has the advantage of reducing longing times.

Please give this a whirl if it is of interest to you.

-- Charles

> ----- Original Message -----
> From: "Charles Manning" <manningc2@actrix.gen.nz>
> To: <yaffs@lists.aleph1.co.uk>
> Cc: "Johan Kotlinski" <johan@teenageengineering.com>
> Sent: Wednesday, February 03, 2010 1:15 AM
> Subject: Re: [Yaffs] multithreading question
>
> > On Tuesday 02 February 2010 00:29:17 Johan Kotlinski wrote:
> >> Hi!
> >> It appears that Yaffs2 multithreading protection is on a very high level
> >> (mutex wrapping entire fread/fwrite calls).
> >
> > Are you talking about yaffs direct or the Linux yaffs?
> > The linux yaffs will be locked on a page-by-page basis and I am going to
> > change the way yaffs direct does the reading/writing too to only lock on
> > a page-by-page basis.
> >
> > The underlying NAND is locked on a apge by page basis too (that's a
> > limitation
> > of the hardware), so is this really a big concern?
> >
> >> My worry is that if a low-priority task does a large fwrite call, it
> >> could
> >> block high-priority tasks for a long time. Is this an acknowledged
> >> problem?
> >
> > It depends on the OS. Some, without priority inhere, won't have this
> > problem.
> >
> >> Are there comparable file systems that handle multithreading in a more
> >> granular way?
>
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