docs/specs/ppc-spapr-numa.rst

12 --------------------------------------------
19 bit 0 of byte 5 of the ibm,architecture-vec-5 property. The format with
20 bit 0 equal to zero is deprecated. The current format, with the bit 0
28     Mem M1 ---- Proc P1    |
29     -----------------      | Socket S1  ---|
32     Mem M2 ---- Proc P2    |               |
33     -----------------      | Socket S2  ---|
46 Relative Performance Distance and ibm,associativity-reference-points
47 --------------------------------------------------------------------
49 The ibm,associativity-reference-points property is an array that is used
53 The definition of its elements also varies with the value of bit 0 of byte 5
54 of the ibm,architecture-vec-5 property. The format with bit 0 equal to zero
56 ibm,associativity-reference-points represents an 1 based ordinal index (i.e.
69 * ibm,associativity-reference-points = {0x3, 0x2, 0x1}
76 means that the second would be 20 and the third level 40. For the P1 and
81   * ibm,associativity-reference-points = {0x3, 0x2, 0x1}
95   P1 and P2 have the same third NUMA level, MOD1: Distance between them = 40
97 Changing the ibm,associativity-reference-points array changes the performance
103   * ibm,associativity-reference-points = {0x2}
123   * ibm,associativity-reference-points = {0x1}
144 provides a common-performance hierarchy,  and the ibm,associativity-reference-points
156 * resources two NUMA levels apart: 40
167 * ibm,associativity-reference-points is set to {0x4, 0x3, 0x2, 0x1}, allowing
170 * ibm,max-associativity-domains supports multiple associativity domains in all
175 These changes are only effective for pseries-5.2 and newer machines that are
178 around for such a long time, with users seeing NUMA distances 10 and 40
189 --------------------------------------------
192 that to the values that the Linux kernel operates on (10, 20, 40, 80, 160).
196 * user distance 31 to 60 will be interpreted as 40
230   0  10  40  80
231   1  40  10  20
241 --------------------------------------
259   0  10  40  20  40
260   1  40  10  80  40
262   3  40  40  20  10
277 * distance from 0 to 1 is 40 (no match at 0x4 and 0x3, will match
280 * distance from 0 to 3 is 40 (no match at 0x4 and 0x3, will match
300 node 1 to 2 is 80, matching at 0x1, and distance from 1 to 3 is 40,
324   0  10  40  20  20
325   1  40  10  40  40
326   2  20  40  10  20
327   3  20  40  20  10
329 Note that this is not what the user wanted - the desired distance between
330 0 and 3 is 40, we calculated it as 20. This is what the current logic and
340 ---------------------------------
349   any A-B pair where the distance back and forth is asymmetric. For example, the
356   0  10  40
360 * 'non-transitive' topologies will be poorly translated to the guest. This is the
367   0  10  20  20  40
368   1  20  10  80  40
370   3  40  40  20  10
372   In the example above, distance 0 to 2 is 20, 2 to 3 is 20, but 0 to 3 is 40.
388 * every other resource, distance: 40
392 the default ibm,associativity-reference-points being used in the pseries
395 ibm,associativity-reference-points = {0x4, 0x4, 0x2}
406   to the same third NUMA level, having distance = 40