Add documentations for linear and logarithmic histogram statistics.
Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 889b19a58b33..bcd3b77fa4e8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5207,6 +5207,9 @@ by a string of size ``name_size``.
#define KVM_STATS_TYPE_CUMULATIVE (0x0 << KVM_STATS_TYPE_SHIFT)
#define KVM_STATS_TYPE_INSTANT (0x1 << KVM_STATS_TYPE_SHIFT)
#define KVM_STATS_TYPE_PEAK (0x2 << KVM_STATS_TYPE_SHIFT)
+ #define KVM_STATS_TYPE_LINEAR_HIST (0x3 << KVM_STATS_TYPE_SHIFT)
+ #define KVM_STATS_TYPE_LOG_HIST (0x4 << KVM_STATS_TYPE_SHIFT)
+ #define KVM_STATS_TYPE_MAX KVM_STATS_TYPE_LOG_HIST
#define KVM_STATS_UNIT_SHIFT 4
#define KVM_STATS_UNIT_MASK (0xF << KVM_STATS_UNIT_SHIFT)
@@ -5214,18 +5217,20 @@ 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_MAX KVM_STATS_UNIT_CYCLES
#define KVM_STATS_BASE_SHIFT 8
#define KVM_STATS_BASE_MASK (0xF << KVM_STATS_BASE_SHIFT)
#define KVM_STATS_BASE_POW10 (0x0 << KVM_STATS_BASE_SHIFT)
#define KVM_STATS_BASE_POW2 (0x1 << KVM_STATS_BASE_SHIFT)
+ #define KVM_STATS_BASE_MAX KVM_STATS_BASE_POW2
struct kvm_stats_desc {
__u32 flags;
__s16 exponent;
__u16 size;
__u32 offset;
- __u32 unused;
+ __u32 bucket_size;
char name[];
};
@@ -5250,6 +5255,21 @@ Bits 0-3 of ``flags`` encode the type:
represents a peak value for a measurement, for example the maximum number
of items in a hash table bucket, the longest time waited and so on.
The corresponding ``size`` field for this type is always 1.
+ * ``KVM_STATS_TYPE_LINEAR_HIST``
+ The statistics data is in the form of linear histogram. The number of
+ buckets is specified by the ``size`` field. The size of buckets is specified
+ by the ``hist_param`` field. The range of the Nth bucket (1 <= N < ``size``)
+ is [``hist_param``*(N-1), ``hist_param``*N), while the range of the last
+ bucket is [``hist_param``*(``size``-1), +INF). (+INF means positive infinity
+ value.) The bucket value indicates how many times the statistics data is in
+ the bucket's range.
+ * ``KVM_STATS_TYPE_LOG_HIST``
+ The statistics data is in the form of logarithmic histogram. The number of
+ buckets is specified by the ``size`` field. The range of the first bucket is
+ [0, 1), while the range of the last bucket is [pow(2, ``size``-2), +INF).
+ Otherwise, The Nth bucket (1 < N < ``size``) covers
+ [pow(2, N-2), pow(2, N-1)). The bucket value indicates how many times the
+ statistics data is in the bucket's range.
Bits 4-7 of ``flags`` encode the unit:
* ``KVM_STATS_UNIT_NONE``
@@ -5282,9 +5302,9 @@ unsigned 64bit data.
The ``offset`` field is the offset from the start of Data Block to the start of
the corresponding statistics data.
-The ``unused`` field is reserved for future support for other types of
-statistics data, like log/linear histogram. Its value is always 0 for the types
-defined above.
+The ``bucket_size`` field is used as a parameter for histogram statistics data.
+It is only used by linear histogram statistics data, specifying the size of a
+bucket.
The ``name`` field is the name string of the statistics data. The name string
starts at the end of ``struct kvm_stats_desc``. The maximum length including
--
2.32.0.402.g57bb445576-goog
