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diff --git a/Documentation/powerpc/vcpudispatch_stats.rst b/Documentation/powerpc/vcpudispatch_stats.rst new file mode 100644 index 000000000000..5704657a5987 --- /dev/null +++ b/Documentation/powerpc/vcpudispatch_stats.rst @@ -0,0 +1,75 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +VCPU Dispatch Statistics +======================== + +For Shared Processor LPARs, the POWER Hypervisor maintains a relatively +static mapping of the LPAR processors (vcpus) to physical processor +chips (representing the "home" node) and tries to always dispatch vcpus +on their associated physical processor chip. However, under certain +scenarios, vcpus may be dispatched on a different processor chip (away +from its home node). + +/proc/powerpc/vcpudispatch_stats can be used to obtain statistics +related to the vcpu dispatch behavior. Writing '1' to this file enables +collecting the statistics, while writing '0' disables the statistics. +By default, the DTLB log for each vcpu is processed 50 times a second so +as not to miss any entries. This processing frequency can be changed +through /proc/powerpc/vcpudispatch_stats_freq. + +The statistics themselves are available by reading the procfs file +/proc/powerpc/vcpudispatch_stats. Each line in the output corresponds to +a vcpu as represented by the first field, followed by 8 numbers. + +The first number corresponds to: + +1. total vcpu dispatches since the beginning of statistics collection + +The next 4 numbers represent vcpu dispatch dispersions: + +2. number of times this vcpu was dispatched on the same processor as last + time +3. number of times this vcpu was dispatched on a different processor core + as last time, but within the same chip +4. number of times this vcpu was dispatched on a different chip +5. number of times this vcpu was dispatches on a different socket/drawer + (next numa boundary) + +The final 3 numbers represent statistics in relation to the home node of +the vcpu: + +6. number of times this vcpu was dispatched in its home node (chip) +7. number of times this vcpu was dispatched in a different node +8. number of times this vcpu was dispatched in a node further away (numa + distance) + +An example output:: + + $ sudo cat /proc/powerpc/vcpudispatch_stats + cpu0 6839 4126 2683 30 0 6821 18 0 + cpu1 2515 1274 1229 12 0 2509 6 0 + cpu2 2317 1198 1109 10 0 2312 5 0 + cpu3 2259 1165 1088 6 0 2256 3 0 + cpu4 2205 1143 1056 6 0 2202 3 0 + cpu5 2165 1121 1038 6 0 2162 3 0 + cpu6 2183 1127 1050 6 0 2180 3 0 + cpu7 2193 1133 1052 8 0 2187 6 0 + cpu8 2165 1115 1032 18 0 2156 9 0 + cpu9 2301 1252 1033 16 0 2293 8 0 + cpu10 2197 1138 1041 18 0 2187 10 0 + cpu11 2273 1185 1062 26 0 2260 13 0 + cpu12 2186 1125 1043 18 0 2177 9 0 + cpu13 2161 1115 1030 16 0 2153 8 0 + cpu14 2206 1153 1033 20 0 2196 10 0 + cpu15 2163 1115 1032 16 0 2155 8 0 + +In the output above, for vcpu0, there have been 6839 dispatches since +statistics were enabled. 4126 of those dispatches were on the same +physical cpu as the last time. 2683 were on a different core, but within +the same chip, while 30 dispatches were on a different chip compared to +its last dispatch. + +Also, out of the total of 6839 dispatches, we see that there have been +6821 dispatches on the vcpu's home node, while 18 dispatches were +outside its home node, on a neighbouring chip. |