17e02586ed
and fix all in-tree references. Architecture-specific documentation is being moved into Documentation/arch/ as a way of cleaning up the top-level documentation directory and making the docs hierarchy more closely match the source hierarchy. Signed-off-by: Costa Shulyupin <costa.shul@redhat.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Link: https://lore.kernel.org/r/20230826165737.2101199-1-costa.shul@redhat.com
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3.0 KiB
ReStructuredText
76 lines
3.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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========================
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VCPU Dispatch Statistics
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========================
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For Shared Processor LPARs, the POWER Hypervisor maintains a relatively
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static mapping of the LPAR processors (vcpus) to physical processor
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chips (representing the "home" node) and tries to always dispatch vcpus
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on their associated physical processor chip. However, under certain
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scenarios, vcpus may be dispatched on a different processor chip (away
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from its home node).
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/proc/powerpc/vcpudispatch_stats can be used to obtain statistics
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related to the vcpu dispatch behavior. Writing '1' to this file enables
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collecting the statistics, while writing '0' disables the statistics.
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By default, the DTLB log for each vcpu is processed 50 times a second so
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as not to miss any entries. This processing frequency can be changed
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through /proc/powerpc/vcpudispatch_stats_freq.
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The statistics themselves are available by reading the procfs file
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/proc/powerpc/vcpudispatch_stats. Each line in the output corresponds to
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a vcpu as represented by the first field, followed by 8 numbers.
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The first number corresponds to:
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1. total vcpu dispatches since the beginning of statistics collection
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The next 4 numbers represent vcpu dispatch dispersions:
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2. number of times this vcpu was dispatched on the same processor as last
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time
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3. number of times this vcpu was dispatched on a different processor core
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as last time, but within the same chip
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4. number of times this vcpu was dispatched on a different chip
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5. number of times this vcpu was dispatches on a different socket/drawer
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(next numa boundary)
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The final 3 numbers represent statistics in relation to the home node of
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the vcpu:
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6. number of times this vcpu was dispatched in its home node (chip)
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7. number of times this vcpu was dispatched in a different node
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8. number of times this vcpu was dispatched in a node further away (numa
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distance)
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An example output::
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$ sudo cat /proc/powerpc/vcpudispatch_stats
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cpu0 6839 4126 2683 30 0 6821 18 0
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cpu1 2515 1274 1229 12 0 2509 6 0
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cpu2 2317 1198 1109 10 0 2312 5 0
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cpu3 2259 1165 1088 6 0 2256 3 0
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cpu4 2205 1143 1056 6 0 2202 3 0
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cpu5 2165 1121 1038 6 0 2162 3 0
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cpu6 2183 1127 1050 6 0 2180 3 0
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cpu7 2193 1133 1052 8 0 2187 6 0
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cpu8 2165 1115 1032 18 0 2156 9 0
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cpu9 2301 1252 1033 16 0 2293 8 0
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cpu10 2197 1138 1041 18 0 2187 10 0
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cpu11 2273 1185 1062 26 0 2260 13 0
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cpu12 2186 1125 1043 18 0 2177 9 0
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cpu13 2161 1115 1030 16 0 2153 8 0
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cpu14 2206 1153 1033 20 0 2196 10 0
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cpu15 2163 1115 1032 16 0 2155 8 0
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In the output above, for vcpu0, there have been 6839 dispatches since
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statistics were enabled. 4126 of those dispatches were on the same
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physical cpu as the last time. 2683 were on a different core, but within
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the same chip, while 30 dispatches were on a different chip compared to
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its last dispatch.
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Also, out of the total of 6839 dispatches, we see that there have been
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6821 dispatches on the vcpu's home node, while 18 dispatches were
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outside its home node, on a neighbouring chip.
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