diff mbox series

[v1,2/4] KVM: stats: Update doc for histogram statistics

Message ID 20210706180350.2838127-3-jingzhangos@google.com
State New
Headers show
Series Linear and Logarithmic histogram statistics | expand

Commit Message

Jing Zhang July 6, 2021, 6:03 p.m. UTC
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@google.com>
---
 Documentation/virt/kvm/api.rst | 36 +++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

Comments

David Matlack July 7, 2021, 11:31 p.m. UTC | #1
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@google.com>
> ---
>  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
>  
>  	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``)
> +    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 <
> +    ``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.
>  
>  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.

This should probably be in a separate patch with a Fixes tag.

Fixes: fdc09ddd4064 ("KVM: stats: Add documentation for binary statistics interface")

> -- 
> 2.32.0.93.g670b81a890-goog
>
Jing Zhang July 8, 2021, 2:29 p.m. UTC | #2
On Wed, Jul 7, 2021 at 6:31 PM David Matlack <dmatlack@google.com> 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@google.com>
> > ---
> >  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
> >
> >       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``)
> > +    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 <
> > +    ``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.
> >
> >  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.
>
> This should probably be in a separate patch with a Fixes tag.
>
> Fixes: fdc09ddd4064 ("KVM: stats: Add documentation for binary statistics interface")
>
> > --
> > 2.32.0.93.g670b81a890-goog
> >
Thanks David.
Jing
David Matlack July 8, 2021, 9:14 p.m. UTC | #3
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@google.com>
> ---
>  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
>
David Matlack July 8, 2021, 9:16 p.m. UTC | #4
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@google.com>
> > ---
> >  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.

> 
> 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
> >
Jing Zhang July 8, 2021, 9:43 p.m. UTC | #5
On Thu, Jul 8, 2021 at 4:16 PM David Matlack <dmatlack@google.com> 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@google.com>
> > > ---
> > >  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
> > >
Paolo Bonzini July 28, 2021, 12:42 p.m. UTC | #6
On 08/07/21 01:31, David Matlack wrote:
>> +
>> +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.
> This should probably be in a separate patch with a Fixes tag.

Generally this chapter (which is probably incomplete, though) only 
includes capabilities for which KVM_CHECK_EXTENSION can return a value 
other than 0 or 1.  So there is no need to include KVM_CAP_STATS_BINARY_FD.

Paolo
Jing Zhang July 30, 2021, 5:32 p.m. UTC | #7
On Wed, Jul 28, 2021 at 5:42 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 08/07/21 01:31, David Matlack wrote:
> >> +
> >> +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.
> > This should probably be in a separate patch with a Fixes tag.
>
> Generally this chapter (which is probably incomplete, though) only
> includes capabilities for which KVM_CHECK_EXTENSION can return a value
> other than 0 or 1.  So there is no need to include KVM_CAP_STATS_BINARY_FD.
Got it. Will drop this change.
>
> Paolo
>
Thanks,
Jing
diff mbox series

Patch

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
 
 	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``)
+    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 <
+    ``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.
 
 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.