[RFC PATCH 0/6] Provide vcpu dispatch statistics

[Naveen N. Rao]

This series adds a new procfs file /proc/powerpc/vcpudispatch_stats for 
providing statistics around how the LPAR processors are dispatched by 
the POWER Hypervisor, in a shared LPAR environment. Patch 6/6 has more 
details on how the statistics are gathered.

An example output:
    $ sudo cat /proc/powerpc/vcpudispatch_stats
    cpu0 6839 4126 0 2683 30 0 6821 18 0
    cpu1 2515 1274 0 1229 12 0 2509 6 0
    cpu2 2317 1198 0 1109 10 0 2312 5 0
    cpu3 2259 1165 0 1088 6 0 2256 3 0
    cpu4 2205 1143 0 1056 6 0 2202 3 0
    cpu5 2165 1121 0 1038 6 0 2162 3 0
    cpu6 2183 1127 0 1050 6 0 2180 3 0
    cpu7 2193 1133 0 1052 8 0 2187 6 0
    cpu8 2165 1115 0 1032 18 0 2156 9 0
    cpu9 2301 1252 0 1033 16 0 2293 8 0
    cpu10 2197 1138 0 1041 18 0 2187 10 0
    cpu11 2273 1185 0 1062 26 0 2260 13 0
    cpu12 2186 1125 0 1043 18 0 2177 9 0
    cpu13 2161 1115 0 1030 16 0 2153 8 0
    cpu14 2206 1153 0 1033 20 0 2196 10 0
    cpu15 2163 1115 0 1032 16 0 2155 8 0

In the output above, for cpu0, we see that there have been 6839 vcpu 
dispatches since statistics were enabled. The next 5 numbers represent 
dispatch dispersions without taking the vcpu home nodes into account.
- 4126 dispatches were on the same physical cpu as the previous time
- 2683 were on a different core, but within the same chip,
- while 30 times, a vcpu was dispatched on a different chip compared to 
  its last dispatch.

The next 3 numbers represent statistics in relation to the vcpu home 
node. We see that there have been 6821 dispatches in the vcpu home node, 
while 18 dispatches were in a different chip.

TODO:
- Consider need for adding cond_resched() in some places.
- More testing, especially on larger machines.


- Naveen

Naveen N. Rao (6):
  powerpc/pseries: Use macros for referring to the DTL enable mask
  powerpc/pseries: Do not save the previous DTL mask value
  powerpc/pseries: Factor out DTL buffer allocation and registration
    routines
  powerpc/pseries: Generalize hcall_vphn()
  powerpc/pseries: Introduce helpers to gatekeep DTLB usage
  powerpc/pseries: Provide vcpu dispatch statistics

 arch/powerpc/include/asm/lppaca.h         |  11 +
 arch/powerpc/include/asm/plpar_wrappers.h |   4 +
 arch/powerpc/include/asm/topology.h       |   4 +
 arch/powerpc/mm/book3s64/vphn.h           |   8 +
 arch/powerpc/mm/numa.c                    | 139 +++++-
 arch/powerpc/platforms/pseries/dtl.c      |  22 +-
 arch/powerpc/platforms/pseries/lpar.c     | 543 +++++++++++++++++++++-
 arch/powerpc/platforms/pseries/setup.c    |  34 +-
 8 files changed, 690 insertions(+), 75 deletions(-)

-- 
2.21.0