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- .. 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.
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