On Thursday, April 04, 2013 12:16:32 pm Andriy Gapon wrote:
> on 19/03/2013 18:20 John Baldwin said the following:
> > Yes, we likely could start using that, we would just need to ensure it has
some
> > sort of minimum size. However, maybe it would always have that minimum
size as you
> > are only going to have additional ranges if you have more than 4GB of RAM
anyway.
> > I think though that there were some odd BIOSes that would place a hole at
15-16MB,
> > and for those the memory region at 1MB is too small. A minimum size of
16MB might
> > handle that case correctly while using the first extended region in the
common
> > case.
>
> How about something like this?
>
> Author: Andriy Gapon <a...@icyb.net.ua>
> Date: Wed Apr 3 11:48:34 2013 +0300
>
> [test] zfsboot: bios_getmem prefer extmem over another random chunk of
high memory
>
> If the extended memory region is sufficiently large.
>
> diff --git a/sys/boot/i386/zfsboot/zfsboot.c
b/sys/boot/i386/zfsboot/zfsboot.c
> index 82402b6..12ceeb0 100644
> --- a/sys/boot/i386/zfsboot/zfsboot.c
> +++ b/sys/boot/i386/zfsboot/zfsboot.c
> @@ -374,6 +374,16 @@ bios_getmem(void)
> }
>
> /*
> + * If extended memory is at least twice as large as the largest
> + * region of higher memory, then carve the high heap out of
> + * extended memory.
> + */
> + if (bios_extmem > 2 * high_heap_size) {
> + high_heap_base = 0x100000 + bios_extmem / 2;
> + high_heap_size = bios_extmem / 2;
> + }
> +
> + /*
> * If we have extended memory and did not find a suitable heap
> * region in the SMAP, use the last 3MB of 'extended' memory as a
> * high heap candidate.
>
We should really use the same algorithm in boot2 and gptboot as well.
I think though that in this case you can just use the last 3MB of heap
rather than half of the extended memory as heap.
--
John Baldwin
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