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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | ======================== | |
4 | VCPU Dispatch Statistics | |
5 | ======================== | |
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6 | |
7 | For Shared Processor LPARs, the POWER Hypervisor maintains a relatively | |
8 | static mapping of the LPAR processors (vcpus) to physical processor | |
9 | chips (representing the "home" node) and tries to always dispatch vcpus | |
10 | on their associated physical processor chip. However, under certain | |
11 | scenarios, vcpus may be dispatched on a different processor chip (away | |
12 | from its home node). | |
13 | ||
14 | /proc/powerpc/vcpudispatch_stats can be used to obtain statistics | |
15 | related to the vcpu dispatch behavior. Writing '1' to this file enables | |
16 | collecting the statistics, while writing '0' disables the statistics. | |
17 | By default, the DTLB log for each vcpu is processed 50 times a second so | |
18 | as not to miss any entries. This processing frequency can be changed | |
19 | through /proc/powerpc/vcpudispatch_stats_freq. | |
20 | ||
21 | The statistics themselves are available by reading the procfs file | |
22 | /proc/powerpc/vcpudispatch_stats. Each line in the output corresponds to | |
23 | a vcpu as represented by the first field, followed by 8 numbers. | |
24 | ||
25 | The first number corresponds to: | |
599448d8 | 26 | |
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27 | 1. total vcpu dispatches since the beginning of statistics collection |
28 | ||
29 | The next 4 numbers represent vcpu dispatch dispersions: | |
599448d8 | 30 | |
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31 | 2. number of times this vcpu was dispatched on the same processor as last |
32 | time | |
33 | 3. number of times this vcpu was dispatched on a different processor core | |
34 | as last time, but within the same chip | |
35 | 4. number of times this vcpu was dispatched on a different chip | |
36 | 5. number of times this vcpu was dispatches on a different socket/drawer | |
599448d8 | 37 | (next numa boundary) |
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38 | |
39 | The final 3 numbers represent statistics in relation to the home node of | |
40 | the vcpu: | |
599448d8 | 41 | |
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42 | 6. number of times this vcpu was dispatched in its home node (chip) |
43 | 7. number of times this vcpu was dispatched in a different node | |
44 | 8. number of times this vcpu was dispatched in a node further away (numa | |
599448d8 MCC |
45 | distance) |
46 | ||
47 | An example output:: | |
2438ac95 | 48 | |
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49 | $ sudo cat /proc/powerpc/vcpudispatch_stats |
50 | cpu0 6839 4126 2683 30 0 6821 18 0 | |
51 | cpu1 2515 1274 1229 12 0 2509 6 0 | |
52 | cpu2 2317 1198 1109 10 0 2312 5 0 | |
53 | cpu3 2259 1165 1088 6 0 2256 3 0 | |
54 | cpu4 2205 1143 1056 6 0 2202 3 0 | |
55 | cpu5 2165 1121 1038 6 0 2162 3 0 | |
56 | cpu6 2183 1127 1050 6 0 2180 3 0 | |
57 | cpu7 2193 1133 1052 8 0 2187 6 0 | |
58 | cpu8 2165 1115 1032 18 0 2156 9 0 | |
59 | cpu9 2301 1252 1033 16 0 2293 8 0 | |
60 | cpu10 2197 1138 1041 18 0 2187 10 0 | |
61 | cpu11 2273 1185 1062 26 0 2260 13 0 | |
62 | cpu12 2186 1125 1043 18 0 2177 9 0 | |
63 | cpu13 2161 1115 1030 16 0 2153 8 0 | |
64 | cpu14 2206 1153 1033 20 0 2196 10 0 | |
65 | cpu15 2163 1115 1032 16 0 2155 8 0 | |
66 | ||
67 | In the output above, for vcpu0, there have been 6839 dispatches since | |
68 | statistics were enabled. 4126 of those dispatches were on the same | |
69 | physical cpu as the last time. 2683 were on a different core, but within | |
70 | the same chip, while 30 dispatches were on a different chip compared to | |
71 | its last dispatch. | |
72 | ||
73 | Also, out of the total of 6839 dispatches, we see that there have been | |
74 | 6821 dispatches on the vcpu's home node, while 18 dispatches were | |
75 | outside its home node, on a neighbouring chip. |