On Tue, Jul 06, 2021 at 06:03:48PM +0000, Jing Zhang wrote:
> Add documentations for linear and logarithmic histogram statistics.
> Add binary stats capability text which is missing during merge of
> the binary stats patch.
>
> Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
> ---
> Documentation/virt/kvm/api.rst | 36 +++++++++++++++++++++++++++++++---
> 1 file changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 3b6e3b1628b4..948d33c26704 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5171,6 +5171,9 @@ 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)
> @@ -5178,11 +5181,13 @@ 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
Should these FOO_MAX additions go in a separate commit too?
>
> struct kvm_stats_desc {
> __u32 flags;
> @@ -5214,6 +5219,22 @@ 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``)
Using 1-based indexes is a little jarring but maybe that's just me :).
> + 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 base of logarithm is
> + specified by the ``hist_param`` field. The range of the Nth bucket (1 < N <
Should 1 be 2 here? The first bucket uses a slightly differen formula as
you mention in the next sentence.
Actually it may be clearer if you re-ordered the sentences a bit:
The range of the first bucket is [0, 1), while the range of the last
bucket is [pow(hist_param, size-1), +INF). Otherwise the Nth bucket
(1-indexed) covers [pow(hist_param, N-2), pow(histparam, N-1)).
> + ``size``) is [pow(``hist_param``, N-2), pow(``hist_param``, N-1)). The range
> + of the first bucket is [0, 1), while the range of the last bucket is
> + [pow(``hist_param``, ``size``-2), +INF). 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``
> @@ -5246,9 +5267,10 @@ 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 ``hist_param`` field is used as a parameter for histogram statistics data.
> +For linear histogram statistics data, it indicates the size of a bucket. For
> +logarithmic histogram statistics data, it indicates the base of the logarithm.
> +Only base of 2 is supported fo logarithmic histogram.
s/fo/for/
>
> 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
> @@ -7182,3 +7204,11 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset
> of the result of KVM_CHECK_EXTENSION. KVM will forward to userspace
> the hypercalls whose corresponding bit is in the argument, and return
> ENOSYS for the others.
> +
> +8.35 KVM_CAP_STATS_BINARY_FD
> +----------------------------
> +
> +:Architectures: all
> +
> +This capability indicates the feature that userspace can get a file descriptor
> +for every VM and VCPU to read statistics data in binary format.
> --
> 2.32.0.93.g670b81a890-goog
>
