Hi Yoan,
On Mon, Apr 19, 2021 at 5:46 AM Yoan Picchi <[email protected]> wrote: > > Hello Jing, and thanks for the patches. Just two small nitpicks. > > On 15/04/2021 16:17, Jing Zhang wrote: > > Signed-off-by: Jing Zhang <[email protected]> > > --- > > Documentation/virt/kvm/api.rst | 169 +++++++++++++++++++++++++++++++++ > > 1 file changed, 169 insertions(+) > > > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > > index 2c4253718881..6474c31a4436 100644 > > --- a/Documentation/virt/kvm/api.rst > > +++ b/Documentation/virt/kvm/api.rst > > @@ -4941,6 +4941,167 @@ see KVM_XEN_VCPU_SET_ATTR above. > > The KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST type may not be used > > with the KVM_XEN_VCPU_GET_ATTR ioctl. > > > > +4.131 KVM_STATS_GETFD > > +--------------------- > > + > > +:Capability: KVM_CAP_STATS_BINARY_FD > > +:Architectures: all > > +:Type: vm ioctl, vcpu ioctl > > +:Parameters: none > > +:Returns: statistics file descriptor on success, < 0 on error > > + > > +Errors: > > + > > + ====== ====================================================== > > + ENOMEM if the fd could not be created due to lack of memory > > + EMFILE if the number of opened files exceeds the limit > > + ====== ====================================================== > > + > > +The file descriptor can be used to read VM/vCPU statistics data in binary > > +format. The file data is organized into three blocks as below: > > ++-------------+ > > +| Header | > > ++-------------+ > > +| Descriptors | > > ++-------------+ > > +| Stats Data | > > ++-------------+ > > + > > +The Header block is always at the start of the file. It is only needed to > > be > > +read one time after a system boot. > > +It is in the form of ``struct kvm_stats_header`` as below:: > > + > > + #define KVM_STATS_ID_MAXLEN 64 > > > Removing one tab would align the 64 with the defines below, though it > might be a tad close to the id field. I'm not sure which is best but > I'll still mention it. Sure, will align it with following defines. > > > > + struct kvm_stats_header { > > + char id[KVM_STATS_ID_MAXLEN]; > > + __u32 name_size; > > + __u32 count; > > + __u32 desc_offset; > > + __u32 data_offset; > > + }; > > + > > +The ``id`` field is identification for the corresponding KVM statistics. > > For > > +KVM statistics, it is in the form of "kvm-{kvm pid}", like "kvm-12345". For > > +VCPU statistics, it is in the form of "kvm-{kvm pid}/vcpu-{vcpu id}", like > > +"kvm-12345/vcpu-12". > > + > > +The ``name_size`` field is the size (byte) of the statistics name string > > +(including trailing '\0') appended to the end of every statistics > > descriptor. > > + > > +The ``count`` field is the number of statistics. > > + > > +The ``desc_offset`` field is the offset of the Descriptors block from the > > start > > +of the file indicated by the file descriptor. > > + > > +The ``data_offset`` field is the offset of the Stats Data block from the > > start > > +of the file indicated by the file descriptor. > > + > > +The Descriptors block is only needed to be read once after a system boot. > > It is > > +an array of ``struct kvm_stats_desc`` as below:: > > + > > + #define KVM_STATS_TYPE_SHIFT 0 > > + #define KVM_STATS_TYPE_MASK (0xF << KVM_STATS_TYPE_SHIFT) > > + #define KVM_STATS_TYPE_CUMULATIVE (0x0 << KVM_STATS_TYPE_SHIFT) > > + #define KVM_STATS_TYPE_INSTANT (0x1 << KVM_STATS_TYPE_SHIFT) > > + #define KVM_STATS_TYPE_MAX KVM_STATS_TYPE_INSTANT > > + > > + #define KVM_STATS_UNIT_SHIFT 4 > > + #define KVM_STATS_UNIT_MASK (0xF << KVM_STATS_UNIT_SHIFT) > > + #define KVM_STATS_UNIT_NONE (0x0 << KVM_STATS_UNIT_SHIFT) > > + #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_SCALE_SHIFT 8 > > + #define KVM_STATS_SCALE_MASK (0xF << KVM_STATS_SCALE_SHIFT) > > + #define KVM_STATS_SCALE_POW10 (0x0 << KVM_STATS_SCALE_SHIFT) > > + #define KVM_STATS_SCALE_POW2 (0x1 << KVM_STATS_SCALE_SHIFT) > > + #define KVM_STATS_SCALE_MAX KVM_STATS_SCALE_POW2 > > + struct kvm_stats_desc { > > + __u32 flags; > > + __s16 exponent; > > + __u16 size; > > + __u32 unused1; > > + __u32 unused2; > > + __u8 name[0]; > > + }; > > > Maybe add a new line between the define and the struct ? And do that as > well in the code ? Thanks. Will add a blank line before both structs. > > > > + > > +The ``flags`` field contains the type and unit of the statistics data > > described > > +by this descriptor. The following flags are supported: > > + * ``KVM_STATS_TYPE_CUMULATIVE`` > > + The statistics data is cumulative. The value of data can only be > > increased. > > + Most of the counters used in KVM are of this type. > > + The corresponding ``count`` filed for this type is always 1. > > + * ``KVM_STATS_TYPE_INSTANT`` > > + The statistics data is instantaneous. Its value can be increased or > > + decreased. This type is usually used as a measurement of some > > resources, > > + like the number of dirty pages, the number of large pages, etc. > > + The corresponding ``count`` field for this type is always 1. > > + * ``KVM_STATS_UNIT_NONE`` > > + There is no unit for the value of statistics data. This usually means > > that > > + the value is a simple counter of an event. > > + * ``KVM_STATS_UNIT_BYTES`` > > + It indicates that the statistics data is used to measure memory size, > > in the > > + unit of Byte, KiByte, MiByte, GiByte, etc. The unit of the data is > > + determined by the ``exponent`` field in the descriptor. The > > + ``KVM_STATS_SCALE_POW2`` flag is valid in this case. The unit of the > > data is > > + determined by ``pow(2, exponent)``. For example, if value is 10, > > + ``exponent`` is 20, which means the unit of statistics data is MiByte, > > we > > + can get the statistics data in the unit of Byte by > > + ``value * pow(2, exponent) = 10 * pow(2, 20) = 10 MiByte`` which is > > + 10 * 1024 * 1024 Bytes. > > + * ``KVM_STATS_UNIT_SECONDS`` > > + It indicates that the statistics data is used to measure time/latency, > > in > > + the unit of nanosecond, microsecond, millisecond and second. The unit > > of the > > + data is determined by the ``exponent`` field in the descriptor. The > > + ``KVM_STATS_SCALE_POW10`` flag is valid in this case. The unit of the > > data > > + is determined by ``pow(10, exponent)``. For example, if value is > > 2000000, > > + ``exponent`` is -6, which means the unit of statistics data is > > microsecond, > > + we can get the statistics data in the unit of second by > > + ``value * pow(10, exponent) = 2000000 * pow(10, -6) = 2 seconds``. > > + * ``KVM_STATS_UNIT_CYCLES`` > > + It indicates that the statistics data is used to measure CPU clock > > cycles. > > + The ``KVM_STATS_SCALE_POW10`` flag is valid in this case. For example, > > if > > + value is 200, ``exponent`` is 4, we can get the number of CPU clock > > cycles > > + by ``value * pow(10, exponent) = 200 * pow(10, 4) = 2000000``. > > + > > +The ``exponent`` field is the scale of corresponding statistics data. It > > has two > > +values as follows: > > + * ``KVM_STATS_SCALE_POW10`` > > + The scale is based on power of 10. It is used for measurement of time > > and > > + CPU clock cycles. > > + * ``KVM_STATS_SCALE_POW2`` > > + The scale is based on power of 2. It is used for measurement of memory > > size. > > + > > +The ``size`` field is the number of values of this statistics data. It is > > in the > > +unit of ``unsigned long`` for VCPU or ``__u64`` for VM. > > + > > +The ``unused1`` and ``unused2`` fields are reserved for future > > +support for other types of statistics data, like log/linear histogram. > > + > > +The ``name`` field points to the name string of the statistics data. The > > name > > +string starts at the end of ``struct kvm_stats_desc``. > > +The maximum length (including trailing '\0') is indicated by ``name_size`` > > +in ``struct kvm_stats_header``. > > + > > +The Stats Data block contains an array of data values of type ``struct > > +kvm_vm_stats_data`` or ``struct kvm_vcpu_stats_data``. It would be read by > > +user space periodically to pull statistics data. > > +The order of data value in Stats Data block is the same as the order of > > +descriptors in Descriptors block. > > + * Statistics data for VM:: > > + > > + struct kvm_vm_stats_data { > > + unsigned long value[0]; > > + }; > > + > > + * Statistics data for VCPU:: > > + > > + struct kvm_vcpu_stats_data { > > + __u64 value[0]; > > + }; > > + > > 5. The kvm_run structure > > ======================== > > > > @@ -6740,3 +6901,11 @@ vcpu_info is set. > > The KVM_XEN_HVM_CONFIG_RUNSTATE flag indicates that the runstate-related > > features KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR/_CURRENT/_DATA/_ADJUST are > > supported by the KVM_XEN_VCPU_SET_ATTR/KVM_XEN_VCPU_GET_ATTR ioctls. > > + > > +8.31 KVM_CAP_STATS_BINARY_FD > > +---------------------------- > > + > > +:Architectures: all > > + > > +This capability indicates the feature that user space can create get a file > > +descriptor for every VM and VCPU to read statistics data in binary format. > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. 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