On 18.03.21 13:03, Oscar Salvador wrote:
On Thu, Mar 18, 2021 at 12:24:16PM +0100, David Hildenbrand wrote:
I don't follow. 2MB == 2MB. And if there would be difference then we would
be in the problem I brought up: vmemmap code allocating too much via the
altmap, which can be very bad because might be populating more vmemmap than
we actually need.
Yes, I meant to say nr_vmemmap_pages won't match, or IOW, won't have the
same meaning.
The end result is the same.
vmemmap_size = 512 * 4KiB = 2 MiB.
That calculation wasn't very useful (/ PAGE_SIZE * PAGE_SIZE)?
Yeah, somewhat redundant.
unsigned long remaining_size = size - vmemmap_size;
And here we could get something like
remaining_size = 2 GiB - 2 MiB
Yes, vmemmap_size would need to scale with nr_sections to be relative to
size.
Just wanted to bring it up, because somene might wonder
"ok, why do we have altmap->nr_pfns = X, and here nr_vmemmap_pages
is Y"
It was an effort to make it consistent, although I see it would bring
more confusion other than anything, so disregard.
I am also unhappy that we have to replicate the same computation at two
places, but I don't see an easy way to avoid that ... we have to trust
on vmemmap code to do the right thing either way :(
--
Thanks,
David / dhildenb
