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| author | Paolo Bonzini <pbonzini@redhat.com> | 2022-07-14 14:27:31 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-07-14 15:01:59 +0300 |
| commit | 1b870fa5573e260bc74d19f381ab0dd971a8d8e7 (patch) | |
| tree | b69d78017e58e7d341c4d56603ce21d488d09c75 /Documentation | |
| parent | 84e7051c0bc1f2a13101553959b3a9d9a8e24939 (diff) | |
| download | linux-1b870fa5573e260bc74d19f381ab0dd971a8d8e7.tar.xz | |
kvm: stats: tell userspace which values are boolean
Some of the statistics values exported by KVM are always only 0 or 1.
It can be useful to export this fact to userspace so that it can track
them specially (for example by polling the value every now and then to
compute a % of time spent in a specific state).
Therefore, add "boolean value" as a new "unit". While it is not exactly
a unit, it walks and quacks like one. In particular, using the type
would be wrong because boolean values could be instantaneous or peak
values (e.g. "is the rmap allocated?") or even two-bucket histograms
(e.g. "number of posted vs. non-posted interrupt injections").
Suggested-by: Amneesh Singh <natto@weirdnatto.in>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 11e00a46c610..48bf6e49a7de 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5657,6 +5657,7 @@ by a string of size ``name_size``. #define KVM_STATS_UNIT_BYTES (0x1 << KVM_STATS_UNIT_SHIFT) #define KVM_STATS_UNIT_SECONDS (0x2 << KVM_STATS_UNIT_SHIFT) #define KVM_STATS_UNIT_CYCLES (0x3 << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_BOOLEAN (0x4 << KVM_STATS_UNIT_SHIFT) #define KVM_STATS_UNIT_MAX KVM_STATS_UNIT_CYCLES #define KVM_STATS_BASE_SHIFT 8 @@ -5724,6 +5725,11 @@ Bits 4-7 of ``flags`` encode the unit: It indicates that the statistics data is used to measure time or latency. * ``KVM_STATS_UNIT_CYCLES`` It indicates that the statistics data is used to measure CPU clock cycles. + * ``KVM_STATS_UNIT_BOOLEAN`` + It indicates that the statistic will always be either 0 or 1. Boolean + statistics of "peak" type will never go back from 1 to 0. Boolean + statistics can be linear histograms (with two buckets) but not logarithmic + histograms. Bits 8-11 of ``flags``, together with ``exponent``, encode the scale of the unit: |