docs/specs/ppc-spapr-numa.rst

15 similar mean performance (or in our context here, distance) relative to
50 to define the relevant performance/distance  related boundaries, defining
60 same performance boundaries are expected to have relative NUMA distance
62 to the same first boundary will have the shortest distance from each
74 belonging to the first NUMA level have distance equal to 10 from each
75 other, and each NUMA level doubles the distance from the previous. This
98 distance attributes for the same associativity arrays, as the following
114   NUMA configuration, distance between them is one boundary above the first
133   P1 and P2 belongs to the same first order boundary. The distance between then
141 how the distances are expressed. The SLIT table provides the NUMA distance
148 The result is that each OS is free to implement and to interpret the distance
150 the distance of the previous level, and the maximum amount of levels is
168   for 4 distinct NUMA distance values based on the NUMA levels
185 is that we needed to translate NUMA distance user input to pseries
188 Translating user distance to kernel distance
191 User input for NUMA distance can vary from 10 to 254. We need to translate
195 * user distance 11 to 30 will be interpreted as 20
196 * user distance 31 to 60 will be interpreted as 40
197 * user distance 61 to 120 will be interpreted as 80
198 * user distance 121 and beyond will be interpreted as 160
199 * user distance 10 stays 10
202 distance (10), keeping it exclusive to the 4th NUMA level (which is still
247 the shortest distance.
275 each distance:
277 * distance from 0 to 1 is 40 (no match at 0x4 and 0x3, will match
279 * distance from 0 to 2 is 20 (no match at 0x4, will match at 0x3)
280 * distance from 0 to 3 is 40 (no match at 0x4 and 0x3, will match
299 in mind that we don't need to revisit node 0 again, the distance from
300 node 1 to 2 is 80, matching at 0x1, and distance from 1 to 3 is 40,
309 In the last step we will analyze just nodes 2 and 3. The desired distance
329 Note that this is not what the user wanted - the desired distance between
342 As mentioned above, the pSeries NUMA distance logic is, in fact, a way to approximate
344 to fully map user input to actual NUMA distance the guest will use. These limitations
348   the distance from node A to B is always the same as B to A. We do not support
349   any A-B pair where the distance back and forth is asymmetric. For example, the
361   kind of topology where the distance from a node A to B is X, B to C is X, but
362   the distance A to C is not X. E.g.:
372   In the example above, distance 0 to 2 is 20, 2 to 3 is 20, but 0 to 3 is 40.
375   nodes. This means that a distance equal to 20 between nodes 0 and 2 and the
376   same distance 20 between nodes 2 and 3 will cause the distance between 0 and 3
386 * local distance, i.e. the distance of the resource to its own NUMA node: 10
387 * if it's a NVLink GPU device, distance: 80
388 * every other resource, distance: 40
401 as far as NUMA distance goes:
406   to the same third NUMA level, having distance = 40
407 * for NVLink GPUs, distance = 80 from everything else