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Diffstat (limited to 'Documentation/driver-api/cxl/allocation/page-allocator.rst')
| -rw-r--r-- | Documentation/driver-api/cxl/allocation/page-allocator.rst | 31 |
1 files changed, 0 insertions, 31 deletions
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 |