On Thu, Jul 8, 2021 at 4:16 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> On Thu, Jul 08, 2021 at 09:14:38PM +0000, David Matlack wrote:
> > 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.
>
> Oops I see you used "<" instead of "<=" so what you have is correct. I
> think reordering the sentences would still be helpfull though.
>
Sure, will reorder the sentences as you suggested.
> >
> > 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
> > >
