[SLOF] [Qemu-ppc] [PATCH v4] board-qemu: add private hcall to inform host on "phandle" update

Segher Boessenkool segher at kernel.crashing.org
Thu Sep 28 18:40:09 AEST 2017

On Thu, Sep 28, 2017 at 07:56:01AM +0200, Thomas Huth wrote:
> On 28.09.2017 06:24, David Gibson wrote:
> > On Wed, Sep 27, 2017 at 12:26:09PM +0200, Thomas Huth wrote:
> >> ... it's likely just yet another slow-down to the boot process.
> >> Linearizing the whole DT in Forth might take a while, I guess.
> > 
> > Do we have to do it in forth?  We could make a C extension to do this,
> > no?
> The device tree lives in Forth, so even if you write the code that
> creates the FDT in C, you have to call back into Forth for each and
> every node and property that you find along the tree. I'm pretty sure it
> won't perform extremely fast...
> Anyway, to give you a number: The FDT->OF-DT conversion (fdt.fs)
> currently takes 350 ms when running SLOF on my Laptop with TCG. I guess
> the other way round will be a bit slower (since the device tree lookup
> has to search through the Forth dictionaries), so I guess we will have
> something around 0.5 seconds in the end. If that slowdown during quiesce
> is acceptable, then go for it! If not, it might be better to search a
> different solution instead.

Converting the device tree to an FDT should take about the same time
as "dev / ls".  How long does that take?

There are no dictionary lookups needed.


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