Commit df63e012 authored by Gregory Price's avatar Gregory Price Committed by Dave Jiang
Browse files

cxl: docs/allocation/hugepages 



Add docs on how CXL capacity interacts with CMA and HugeTLB allocation
interfaces.

Signed-off-by: default avatarGregory Price <gourry@gourry.net>
Link: https://patch.msgid.link/20250512162134.3596150-17-gourry@gourry.net


Signed-off-by: default avatarDave Jiang <dave.jiang@intel.com>
parent f109e77d

Documentation/driver-api/cxl/allocation/hugepages.rst

0 → 100644
+32 −0
Original line number Diff line number Diff line 
.. SPDX-License-Identifier: GPL-2.0



==========

Huge Pages

==========



Contiguous Memory Allocator

===========================

CXL Memory onlined as SystemRAM during early boot is eligible for use by CMA,

as the NUMA node hosting that capacity will be `Online` at the time CMA

carves out contiguous capacity.



CXL Memory deferred to the CXL Driver for configuration cannot have its

capacity allocated by CMA - as the NUMA node hosting the capacity is `Offline`

at :code:`__init` time - when CMA carves out contiguous capacity.



HugeTLB

=======

Different huge page sizes allow different memory configurations.



2MB Huge Pages

--------------

All CXL capacity regardless of configuration time or memory zone is eligible

for use as 2MB huge pages.



1GB Huge Pages

--------------

CXL capacity onlined in :code:`ZONE_NORMAL` is eligible for 1GB Gigantic Page

allocation.



CXL capacity onlined in :code:`ZONE_MOVABLE` is not eligible for 1GB Gigantic

Page allocation.

Documentation/driver-api/cxl/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -47,5 +47,6 @@ that have impacts on each other. The docs here break up configurations steps. 
   allocation/dax

   allocation/page-allocator

   allocation/reclaim

   allocation/hugepages.rst



.. only::  subproject and html