On Mon, Oct 16, 2017 at 04:49:17PM +1100, Alexey Kardashevskiy wrote: > At the moment, on 256CPU + 256 PCI devices guest, it takes the guest > about 8.5sec to read the entire device tree. Some explanation can be > found here: https://patchwork.ozlabs.org/patch/826124/ but mostly it is > because the kernel traverses the tree twice and it calls "getprop" for > each properly which is really SLOF as it searches from the linked list > beginning every time. > > Since SLOF has just learned to build FDT and this takes less than 0.5sec > for such a big guest, this makes use of the proposed client interface > method - "fdt-fetch". > > If "fdt-fetch" is not available, the old method is used. > > Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
I like the concept, few details though..
> ---
> arch/powerpc/kernel/prom_init.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index 02190e90c7ae..daa50a153737 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -2498,6 +2498,31 @@ static void __init flatten_device_tree(void)
> prom_panic("Can't allocate initial device-tree chunk\n");
> mem_end = mem_start + room;
>
> + if (!call_prom_ret("fdt-fetch", 2, 1, NULL, mem_start,
> + room - sizeof(mem_reserve_map))) {
> + u32 size;
> +
> + hdr = (void *) mem_start;
> +
> + /* Fixup the boot cpuid */
> + hdr->boot_cpuid_phys = cpu_to_be32(prom.cpu);
If SLOF is generating a tree it really should get this header field
right as well.
> + /* Append the reserved map to the end of the blob */
> + hdr->off_mem_rsvmap = hdr->totalsize;
> + size = be32_to_cpu(hdr->totalsize);
> + rsvmap = (void *) hdr + size;
> + hdr->totalsize = cpu_to_be32(size + sizeof(mem_reserve_map));
> + memcpy(rsvmap, mem_reserve_map, sizeof(mem_reserve_map));
.. and the reserve map for that matter. I don't really understand
what you're doing here. Note also that the reserve map is required to
be 8-byte aligned, which totalsize might not be.
> + /* Store the DT address */
> + dt_header_start = mem_start;
> +
> +#ifdef DEBUG_PROM
> + prom_printf("Fetched DTB: %d bytes to @%x\n", size, mem_start);
> +#endif
> + goto print_exit;
> + }
> +
> /* Get root of tree */
> root = call_prom("peer", 1, 1, (phandle)0);
> if (root == (phandle)0)
> @@ -2548,6 +2573,7 @@ static void __init flatten_device_tree(void)
> /* Copy the reserve map in */
> memcpy(rsvmap, mem_reserve_map, sizeof(mem_reserve_map));
>
> +print_exit:
> #ifdef DEBUG_PROM
> {
> int i;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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