diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-cxl | 11 | ||||
| -rw-r--r-- | Documentation/driver-api/cxl/allocation/page-allocator.rst | 31 |
2 files changed, 10 insertions, 32 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl index 6b4e8c7a963d..c80a1b5a03db 100644 --- a/Documentation/ABI/testing/sysfs-bus-cxl +++ b/Documentation/ABI/testing/sysfs-bus-cxl @@ -496,8 +496,17 @@ Description: changed, only freed by writing 0. The kernel makes no guarantees that data is maintained over an address space freeing event, and there is no guarantee that a free followed by an allocate - results in the same address being allocated. + results in the same address being allocated. If extended linear + cache is present, the size indicates extended linear cache size + plus the CXL region size. +What: /sys/bus/cxl/devices/regionZ/extended_linear_cache_size +Date: October, 2025 +KernelVersion: v6.19 +Contact: linux-cxl@vger.kernel.org +Description: + (RO) The size of extended linear cache, if there is an extended + linear cache. Otherwise the attribute will not be visible. What: /sys/bus/cxl/devices/regionZ/mode Date: January, 2023 diff --git a/Documentation/driver-api/cxl/allocation/page-allocator.rst b/Documentation/driver-api/cxl/allocation/page-allocator.rst index 7b8fe1b8d5bb..3fa584a248bd 100644 --- a/Documentation/driver-api/cxl/allocation/page-allocator.rst +++ b/Documentation/driver-api/cxl/allocation/page-allocator.rst @@ -41,37 +41,6 @@ To simplify this, the page allocator will prefer :code:`ZONE_MOVABLE` over will fallback to allocate from :code:`ZONE_NORMAL`. -Zone and Node Quirks -==================== -Let's consider a configuration where the local DRAM capacity is largely onlined -into :code:`ZONE_NORMAL`, with no :code:`ZONE_MOVABLE` capacity present. The -CXL capacity has the opposite configuration - all onlined in -:code:`ZONE_MOVABLE`. - -Under the default allocation policy, the page allocator will completely skip -:code:`ZONE_MOVABLE` as a valid allocation target. This is because, as of -Linux v6.15, the page allocator does (approximately) the following: :: - - for (each zone in local_node): - - for (each node in fallback_order): - - attempt_allocation(gfp_flags); - -Because the local node does not have :code:`ZONE_MOVABLE`, the CXL node is -functionally unreachable for direct allocation. As a result, the only way -for CXL capacity to be used is via `demotion` in the reclaim path. - -This configuration also means that if the DRAM ndoe has :code:`ZONE_MOVABLE` -capacity - when that capacity is depleted, the page allocator will actually -prefer CXL :code:`ZONE_MOVABLE` pages over DRAM :code:`ZONE_NORMAL` pages. - -We may wish to invert this priority in future Linux versions. - -If `demotion` and `swap` are disabled, Linux will begin to cause OOM crashes -when the DRAM nodes are depleted. See the reclaim section for more details. - - CGroups and CPUSets =================== Finally, assuming CXL memory is reachable via the page allocation (i.e. onlined |