On 6 Aug 2021, at 11:16, Vlastimil Babka wrote:

On 8/5/21 9:02 PM, Zi Yan wrote:

quoted

From: Zi Yan <ziy@nvidia.com>
+config SET_MAX_ORDER
+	int "Set maximum order of buddy allocator"
+    depends on SPARSEMEM_VMEMMAP && (ARCH_FORCE_MAX_ORDER = 0)
+	range 11 255
+	default "11"
+	help
+	  The kernel memory allocator divides physically contiguous memory
+	  blocks into "zones", where each zone is a power of two number of
+	  pages.  This option selects the largest power of two that the kernel
+	  keeps in the memory allocator.  If you need to allocate very large
+	  blocks of physically contiguous memory, then you may need to
+	  increase this value.
+
+	  This config option is actually maximum order plus one. For example,
+	  a value of 11 means that the largest free memory block is 2^10 pages.

It's enough that it's confusing for the devs, we could spare the users and add
+1 to the value they specify :)

Sure. I will change the existing ARCH_FORCE_MAX_ORDER too, otherwise people might
get confused by two different MAX_ORDERs. Since this Kconfig only appears when
ARCH_FORCE_MAX_ORDER is not specified.


—
Best Regards,
Yan, Zi