This patchset adds linear and logarithmic histogram stats support and extend some halt polling stats with histogram. Histogram stats is very useful when we need to know the distribution of some latencies or any other stuff like used memory size, huge page size, etc. Below is a snapshot for three logarithmic histogram stats added in this patchset. halt_poll_success_hist shows the distribution of wait time before a success polling. halt_poll_fail_hist shows the distribution of wait time before a fail polling. halt_wait_hist shows the distribution of wait time of a VCPU spending on wait after it is halted. The halt polling parameters is halt_poll_ns = 500000, halt_poll_ns_grow = 2, halt_poll_ns_grow_start = 10000, halt_poll_ns_shrink = 2; >From the snapshot, not only we can get an intuitive overview of those latencies, but also we can tune the polling parameters based on this; For example, it shows that about 80% of successful polling is less than 132000 nanoseconds from halt_poll_success_hist, then it might be a good option to set halt_poll_ns as 132000 instead of 500000. halt_poll_success_hist: Range Bucket Value Percent Cumulative Percent [0, 1) 0 0.000% 0.000% [1, 2) 0 0.000% 0.000% [2, 4) 0 0.000% 0.000% [4, 8) 0 0.000% 0.000% [8, 16) 0 0.000% 0.000% [16, 32) 0 0.000% 0.000% [32, 64) 0 0.000% 0.000% [64, 128) 0 0.000% 0.000% [128, 256) 3 0.093% 0.093% [256, 512) 21 0.650% 0.743% [512, 1024) 43 1.330% 2.073% [1024, 2048) 279 8.632% 10.705% [2048, 4096) 253 7.828% 18.533% [4096, 8192) 595 18.410% 36.943% [8192, 16384) 274 8.478% 45.421% [16384, 32768) 351 10.860% 56.281% [32768, 65536) 343 10.613% 66.894% [65536, 131072) 421 13.026% 79.920% [131072, 262144) 459 14.202% 94.121% [262144, 524288) 190 5.879% 100.000% halt_poll_fail_hist: Range Bucket Value Percent Cumulative Percent [0, 1) 0 0.000% 0.000% [1, 2) 0 0.000% 0.000% [2, 4) 0 0.000% 0.000% [4, 8) 0 0.000% 0.000% [8, 16) 0 0.000% 0.000% [16, 32) 0 0.000% 0.000% [32, 64) 0 0.000% 0.000% [64, 128) 21 0.529% 0.529% [128, 256) 398 10.020% 10.549% [256, 512) 613 15.433% 25.982% [512, 1024) 437 11.002% 36.984% [1024, 2048) 264 6.647% 43.630% [2048, 4096) 302 7.603% 51.234% [4096, 8192) 350 8.812% 60.045% [8192, 16384) 488 12.286% 72.331% [16384, 32768) 258 6.495% 78.827% [32768, 65536) 227 5.715% 84.542% [65536, 131072) 232 5.841% 90.383% [131072, 262144) 246 6.193% 96.576% [262144, 524288) 136 3.424% 100.000% halt_wait_hist: Range Bucket Value Percent Cumulative Percent [0, 1) 0 0.000% 0.000% [1, 2) 0 0.000% 0.000% [2, 4) 0 0.000% 0.000% [4, 8) 0 0.000% 0.000% [8, 16) 0 0.000% 0.000% [16, 32) 0 0.000% 0.000% [32, 64) 0 0.000% 0.000% [64, 128) 0 0.000% 0.000% [128, 256) 0 0.000% 0.000% [256, 512) 0 0.000% 0.000% [512, 1024) 0 0.000% 0.000% [1024, 2048) 0 0.000% 0.000% [2048, 4096) 7 0.127% 0.127% [4096, 8192) 37 0.671% 0.798% [8192, 16384) 69 1.251% 2.049% [16384, 32768) 94 1.704% 3.753% [32768, 65536) 150 2.719% 6.472% [65536, 131072) 233 4.224% 10.696% [131072, 262144) 276 5.004% 15.700% [262144, 524288) 236 4.278% 19.978% [524288, 1.04858e+06) 176 3.191% 23.169% [1.04858e+06, 2.09715e+06) 94 16.207% 39.376% [2.09715e+06, 4.1943e+06) 1667 30.221% 69.598% [4.1943e+06, 8.38861e+06) 825 14.956% 84.554% [8.38861e+06, 1.67772e+07) 111 2.012% 86.566% [1.67772e+07, 3.35544e+07) 76 1.378% 87.944% [3.35544e+07, 6.71089e+07) 65 1.178% 89.123% [6.71089e+07, 1.34218e+08) 161 2.919% 92.041% [1.34218e+08, 2.68435e+08) 250 4.532% 96.574% [2.68435e+08, 5.36871e+08) 188 3.408% 99.982% [5.36871e+08, 1.07374e+09) 1 0.018% 100.000% --- Jing Zhang (4): KVM: stats: Support linear and logarithmic histogram statistics KVM: stats: Update doc for histogram statistics KVM: selftests: Add checks for histogram stats parameters KVM: stats: Add halt polling related histogram stats Documentation/virt/kvm/api.rst | 36 ++++++++++- arch/arm64/kvm/guest.c | 4 -- arch/mips/kvm/mips.c | 4 -- arch/powerpc/include/asm/kvm_host.h | 1 - arch/powerpc/kvm/book3s.c | 5 -- arch/powerpc/kvm/book3s_hv.c | 20 +++++- arch/powerpc/kvm/booke.c | 5 -- arch/s390/kvm/kvm-s390.c | 4 -- arch/x86/kvm/x86.c | 4 -- include/linux/kvm_host.h | 62 ++++++++++++++----- include/linux/kvm_types.h | 20 ++++++ include/uapi/linux/kvm.h | 11 +++- .../selftests/kvm/kvm_binary_stats_test.c | 17 +++++ virt/kvm/binary_stats.c | 36 +++++++++++ virt/kvm/kvm_main.c | 19 ++++++ 15 files changed, 196 insertions(+), 52 deletions(-) base-commit: 7caa04b36f204a01dac65582b71d26d190a1e022 -- 2.32.0.93.g670b81a890-goog
