Re: [PATCH v5 09/10] qmp: add filtering of statistics by name

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Paolo Bonzini (pbonzini@redhat.com) wrote:
> Allow retrieving only a subset of statistics.  This can be useful
> for example in order to plot a subset of the statistics many times
> a second.
> 
> KVM publishes ~40 statistics for each vCPU on x86; retrieving and
> serializing all of them would be useless
> 
> Another use will be in HMP in the following patch; implementing the
> filter in the backend is easy enough that it was deemed okay to make
> this a public interface.
> 
> Example:
> 
> { "execute": "query-stats",
>   "arguments": {
>     "target": "vcpu",
>     "vcpus": [ "/machine/unattached/device[2]",
>                "/machine/unattached/device[4]" ],
>     "providers": [
>       { "provider": "kvm",
>         "names": [ "l1d_flush", "exits" ] } } }
> 
> { "return": {
>     "vcpus": [
>       { "path": "/machine/unattached/device[2]"
>         "providers": [
>           { "provider": "kvm",
>             "stats": [ { "name": "l1d_flush", "value": 41213 },
>                        { "name": "exits", "value": 74291 } ] } ] },
>       { "path": "/machine/unattached/device[4]"
>         "providers": [
>           { "provider": "kvm",
>             "stats": [ { "name": "l1d_flush", "value": 16132 },
>                        { "name": "exits", "value": 57922 } ] } ] } ] } }
> 
> Extracted from a patch by Mark Kanda.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  accel/kvm/kvm-all.c     | 17 +++++++++++------
>  include/monitor/stats.h |  2 +-
>  monitor/qmp-cmds.c      |  7 ++++++-
>  qapi/stats.json         |  6 +++++-
>  4 files changed, 23 insertions(+), 9 deletions(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 66c4ac1ac6..f90f0602bc 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2312,7 +2312,7 @@ bool kvm_dirty_ring_enabled(void)
>  }
>  
>  static void query_stats_cb(StatsResultList **result, StatsTarget target,
> -                           strList *targets, Error **errp);
> +                           strList *names, strList *targets, Error **errp);
>  static void query_stats_schemas_cb(StatsSchemaList **result, Error **errp);
>  
>  static int kvm_init(MachineState *ms)
> @@ -3713,6 +3713,7 @@ typedef struct StatsArgs {
>          StatsResultList **stats;
>          StatsSchemaList **schema;
>      } result;
> +    strList *names;
>      Error **errp;
>  } StatsArgs;
>  
> @@ -3921,7 +3922,7 @@ static StatsDescriptors *find_stats_descriptors(StatsTarget target, int stats_fd
>  }
>  
>  static void query_stats(StatsResultList **result, StatsTarget target,
> -                        int stats_fd, Error **errp)
> +                        strList *names, int stats_fd, Error **errp)
>  {
>      struct kvm_stats_desc *kvm_stats_desc;
>      struct kvm_stats_header *kvm_stats_header;
> @@ -3963,6 +3964,9 @@ static void query_stats(StatsResultList **result, StatsTarget target,
>  
>          /* Add entry to the list */
>          stats = (void *)stats_data + pdesc->offset;
> +        if (!apply_str_list_filter(pdesc->name, names)) {
> +            continue;
> +        }
>          stats_list = add_kvmstat_entry(pdesc, stats, stats_list, errp);
>      }
>  
> @@ -4024,8 +4028,8 @@ static void query_stats_vcpu(CPUState *cpu, run_on_cpu_data data)
>          error_propagate(kvm_stats_args->errp, local_err);
>          return;
>      }
> -    query_stats(kvm_stats_args->result.stats, STATS_TARGET_VCPU, stats_fd,
> -                kvm_stats_args->errp);
> +    query_stats(kvm_stats_args->result.stats, STATS_TARGET_VCPU,
> +                kvm_stats_args->names, stats_fd, kvm_stats_args->errp);
>      close(stats_fd);
>  }
>  
> @@ -4046,7 +4050,7 @@ static void query_stats_schema_vcpu(CPUState *cpu, run_on_cpu_data data)
>  }
>  
>  static void query_stats_cb(StatsResultList **result, StatsTarget target,
> -                           strList *targets, Error **errp)
> +                           strList *names, strList *targets, Error **errp)
>  {
>      KVMState *s = kvm_state;
>      CPUState *cpu;
> @@ -4060,7 +4064,7 @@ static void query_stats_cb(StatsResultList **result, StatsTarget target,
>              error_setg_errno(errp, errno, "KVM errno, stats: ioctl failed");
>              return;
>          }
> -        query_stats(result, target, stats_fd, errp);
> +        query_stats(result, target, names, stats_fd, errp);
>          close(stats_fd);
>          break;
>      }
> @@ -4068,6 +4072,7 @@ static void query_stats_cb(StatsResultList **result, StatsTarget target,
>      {
>          StatsArgs stats_args;
>          stats_args.result.stats = result;
> +        stats_args.names = names;
>          stats_args.errp = errp;
>          CPU_FOREACH(cpu) {
>              if (!apply_str_list_filter(cpu->parent_obj.canonical_path, targets)) {
> diff --git a/include/monitor/stats.h b/include/monitor/stats.h
> index 80a523dd29..fcf0983154 100644
> --- a/include/monitor/stats.h
> +++ b/include/monitor/stats.h
> @@ -11,7 +11,7 @@
>  #include "qapi/qapi-types-stats.h"
>  
>  typedef void StatRetrieveFunc(StatsResultList **result, StatsTarget target,
> -                              strList *targets, Error **errp);
> +                              strList *names, strList *targets, Error **errp);
>  typedef void SchemaRetrieveFunc(StatsSchemaList **result, Error **errp);
>  
>  /*
> diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
> index e49ab345d7..7314cd813d 100644
> --- a/monitor/qmp-cmds.c
> +++ b/monitor/qmp-cmds.c
> @@ -472,12 +472,17 @@ static bool invoke_stats_cb(StatsCallbacks *entry,
>                              Error **errp)
>  {
>      strList *targets = NULL;
> +    strList *names = NULL;
>      ERRP_GUARD();
>  
>      if (request) {
>          if (request->provider != entry->provider) {
>              return true;
>          }
> +        if (request->has_names && !request->names) {
> +            return true;
> +        }
> +        names = request->has_names ? request->names : NULL;
>      }
>  
>      switch (filter->target) {
> @@ -496,7 +501,7 @@ static bool invoke_stats_cb(StatsCallbacks *entry,
>          abort();
>      }
>  
> -    entry->stats_cb(stats_results, filter->target, targets, errp);
> +    entry->stats_cb(stats_results, filter->target, names, targets, errp);
>      if (*errp) {
>          qapi_free_StatsResultList(*stats_results);
>          *stats_results = NULL;
> diff --git a/qapi/stats.json b/qapi/stats.json
> index 503918ea4c..2f8bfe8fdb 100644
> --- a/qapi/stats.json
> +++ b/qapi/stats.json
> @@ -75,11 +75,14 @@
>  # Indicates a set of statistics that should be returned by query-stats.
>  #
>  # @provider: provider for which to return statistics.
> +
> +# @names: statistics to be returned (all if omitted).
>  #
>  # Since: 7.1
>  ##
>  { 'struct': 'StatsRequest',
> -  'data': { 'provider': 'StatsProvider' } }
> +  'data': { 'provider': 'StatsProvider',
> +            '*names': [ 'str' ] } }
>  
>  ##
>  # @StatsVCPUFilter:
> @@ -99,6 +102,7 @@
>  # that target:
>  # - which vCPUs to request statistics for
>  # - which providers to request statistics from
> +# - which named values to return within each provider
>  #
>  # Since: 7.1
>  ##
> -- 
> 2.36.1
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK