On 03/01/2016 03:06 AM, Dan Williams wrote:
On Mon, Feb 29, 2016 at 4:06 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote:
On 29.2.2016 18:55, Dan Williams wrote:
On Mon, Feb 29, 2016 at 4:33 AM, Vlastimil Babka <vbabka@xxxxxxx> wrote:
On 02/02/2016 06:42 AM, Andrew Morton wrote:
In this case it's already part of the equation because:
config ZONE_DEVICE
depends on MEMORY_HOTPLUG
depends on MEMORY_HOTREMOVE
...and those in turn depend on SPARSEMEM.
Fine, but then SPARSEMEM_VMEMMAP should be still an available subvariant of
SPARSEMEM with SECTION_WIDTH=0.
It should be, but not for the ZONE_DEVICE case. ZONE_DEVICE depends
on x86_64 which means ZONE_DEVICE also implies SPARSEMEM_VMEMMAP
since:
config ARCH_SPARSEMEM_ENABLE
def_bool y
depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
select SPARSEMEM_STATIC if X86_32
select SPARSEMEM_VMEMMAP_ENABLE if X86_64
Now, if a future patch wants to reclaim page flags space for other
usages outside of ZONE_DEVICE it can do the work to handle the
SPARSEMEM_VMEMMAP=n case. I don't see a reason to fold that
distinction into the current patch given the current constraints.
OK so that IUUC shows that x86_64 should be always fine without decreasing the
range for NODES_SHIFT? That's basically my point - since there's a configuration
where things don't fit (32bit?), the patch broadly decreases range for
NODES_SHIFT for everyone, right?
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