Paolo Bonzini <pbonz...@redhat.com> writes:
> 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 <pbonz...@redhat.com>
> ---
> v3->v4: handle empty filter early by avoiding the query altogether
>
> accel/kvm/kvm-all.c | 17 +++++++++++------
> include/monitor/stats.h | 4 ++--
> monitor/qmp-cmds.c | 16 +++++++++++++---
> qapi/stats.json | 6 +++++-
> 4 files changed, 31 insertions(+), 12 deletions(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 461b6cf927..a61d17719e 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2311,7 +2311,7 @@ bool kvm_dirty_ring_enabled(void)
> return kvm_state->kvm_dirty_ring_size ? true : false;
> }
>
> -static void query_stats_cb(StatsResultList **result, StatsTarget target,
> +static void query_stats_cb(StatsResultList **result, StatsTarget target,
> strList *names,
Long line.
> strList *targets, Error **errp);
> static void query_stats_schemas_cb(StatsSchemaList **result, Error **errp);
>
> @@ -3713,6 +3713,7 @@ typedef struct StatsArgs {
> StatsResultList **stats;
> StatsSchemaList **schema;
> } result;
> + strList *names;
> Error **errp;
> } StatsArgs;
>
> @@ -3926,7 +3927,7 @@ static StatsDescriptors
> *find_stats_descriptors(StatsTarget target, int stats_fd
> return descriptors;
> }
>
> -static void query_stats(StatsResultList **result, StatsTarget target,
> +static void query_stats(StatsResultList **result, StatsTarget target,
> strList *names,
Long line.
> int stats_fd, Error **errp)
> {
> struct kvm_stats_desc *kvm_stats_desc;
> @@ -3969,6 +3970,9 @@ 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);
> }
>
> @@ -4030,8 +4034,8 @@ 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);
> }
>
> @@ -4052,7 +4056,7 @@ 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;
> @@ -4066,7 +4070,7 @@ static void query_stats_cb(StatsResultList **result,
> StatsTarget target,
> error_setg(errp, "KVM stats: ioctl failed");
> return;
> }
> - query_stats(result, target, stats_fd, errp);
> + query_stats(result, target, names, stats_fd, errp);
> close(stats_fd);
> break;
> }
> @@ -4074,6 +4078,7 @@ 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 840c4ed08e..88f046f568 100644
> --- a/include/monitor/stats.h
> +++ b/include/monitor/stats.h
> @@ -11,8 +11,8 @@
> #include "qapi/qapi-types-stats.h"
>
> typedef void StatRetrieveFunc(StatsResultList **result, StatsTarget target,
> - strList *targets, Error **errp);
> -typedef void SchemaRetrieveFunc(StatsSchemaList **result, Error **errp);
> + strList *names, strList *targets, Error
> **errp);
> +typedef void SchemaRetrieveFunc(StatsSchemaList **, Error **);
Did you drop the parameter names intentionally?
>
> /*
> * Register callbacks for the QMP query-stats command.
> diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
> index 7be0e7414a..e822f1b0a9 100644
> --- a/monitor/qmp-cmds.c
> +++ b/monitor/qmp-cmds.c
> @@ -467,15 +467,24 @@ void add_stats_callbacks(StatsProvider provider,
> }
>
> static bool stats_provider_requested(StatsProvider provider,
> - StatsFilter *filter)
> + StatsFilter *filter,
> + strList **p_names)
> {
> StatsRequestList *request;
>
> + *p_names = NULL;
> if (!filter->has_providers) {
> return true;
> }
> for (request = filter->providers; request; request = request->next) {
> if (request->value->provider == provider) {
> + if (request->value->has_names) {
> + if (!request->value->names) {
> + /* No names allowed is the same as skipping the
> provider. */
Long line.
> + return false;
Any other elements of filter->providers that match @provider will be
silently ignored. Is this what you want?
Uh, do we leak @p_names if earlier elements matched?
> + }
> + *p_names = request->value->names;
> + }
> return true;
> }
> }
> @@ -506,8 +515,9 @@ StatsResultList *qmp_query_stats(StatsFilter *filter,
> Error **errp)
> }
>
> QTAILQ_FOREACH(entry, &stats_callbacks, next) {
> - if (stats_provider_requested(entry->provider, filter)) {
> - entry->stats_cb(&stats_results, filter->target, targets, errp);
> + strList *names = NULL;
> + if (stats_provider_requested(entry->provider, filter, &names)) {
> + entry->stats_cb(&stats_results, filter->target, names, targets,
> errp);
Brain cramp (broken night)... where is @names freed?
Long line.
> if (*errp) {
> qapi_free_StatsResultList(stats_results);
> return NULL;
> diff --git a/qapi/stats.json b/qapi/stats.json
> index b75bb86124..2dbf188d36 100644
> --- a/qapi/stats.json
> +++ b/qapi/stats.json
> @@ -74,11 +74,14 @@
> # 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:
> @@ -98,6 +101,7 @@
> # that target:
> # - which vCPUs to request statistics for
> # - which provider to request statistics from
Should this be "which providers"?
> +# - which values to return within each provider
This is member @provider sub-member @names. Hmm. "which named values
to return"?
> #
> # Since: 7.1
> ##
