Re: [PATCH 1/3] qemu_monitor: add qemuMonitorQueryStats

[Martin Kletzander <mkletzan@xxxxxxxxxx>]

On Thu, Jul 14, 2022 at 11:22:02AM +0530, Amneesh Singh wrote:
> Related: https://gitlab.com/libvirt/libvirt/-/issues/276
>
> This patch adds an API for the "query-stats" QMP command.
>
> The query returns a JSON containing the statistics based on the target,
> which can either be vCPU or VM, and the providers. The API deserializes
> the query result into an array of GHashMaps, which can later be used to
> extract all the query statistics. GHashMaps are used to avoid traversing
> the entire array to find the statistics you are looking for. This would
> be a singleton array if the target is a VM since the returned JSON is
> also a singleton array in that case.
>
> Signed-off-by: Amneesh Singh <natto@xxxxxxxxxxxxx>
> ---
> src/qemu/qemu_monitor.c      |  70 +++++++++++++++++++
> src/qemu/qemu_monitor.h      |  45 ++++++++++++
> src/qemu/qemu_monitor_json.c | 130 +++++++++++++++++++++++++++++++++++
> src/qemu/qemu_monitor_json.h |   6 ++
> 4 files changed, 251 insertions(+)
>
> diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
> index 80696de7..4e228bfb 100644
> --- a/src/qemu/qemu_monitor_json.c
> +++ b/src/qemu/qemu_monitor_json.c
> @@ -9031,3 +9031,133 @@ qemuMonitorJSONMigrateRecover(qemuMonitor *mon,
>
>     return qemuMonitorJSONCheckError(cmd, reply);
> }
> +
> +static GPtrArray *
> +qemuMonitorJSONExtractQueryStats(virJSONValue *arr)
> +{
> +    g_autoptr(GPtrArray) queried_stats = NULL;
> +    size_t nstats = virJSONValueArraySize(arr);
> +    size_t i;
> +
> +    /* Create a GPtrArray for GHashTables */
> +    queried_stats = g_ptr_array_new_full(nstats, (GDestroyNotify) g_hash_table_destroy);
> +
> +    for (i = 0; i < nstats; i++) {
> +        virJSONValue *obj = virJSONValueArrayGet(arr, i);
> +        virJSONValue *stats = virJSONValueObjectGetArray(obj, "stats");
> +        size_t j;
> +
> +        /* Create a GHashTable for virJSONValues */
> +        GHashTable *hash_table = virHashNew((GDestroyNotify) virJSONValueFree);
> +
> +        for (j = 0; j < virJSONValueArraySize(stats); j++) {
> +            virJSONValue *stat = virJSONValueArrayGet(stats, j);
> +
> +            g_hash_table_insert(hash_table,
> +                                g_strdup(virJSONValueObjectGetString(stat, "name")),
> +                                virJSONValueObjectGet(stat, "value"));
> +        }
> +
> +        g_ptr_array_add(queried_stats, hash_table);
> +    }
> +
> +    return g_steal_pointer(&queried_stats);
> +}
> +
> +
> +/**
> + * qemuMonitorJSONQueryStats:
> + * @mon: monitor object
> + * @target: the target type for the query
> + * @vcpus: a list of vCPU QOM paths for filtering the statistics
> + * @providers: an array of providers to filter statistics
> + *
> + * @vcpus is a NULL terminated array of strings. @providers is a GPtrArray
> + * for qemuMonitorQueryStatsProvider.
> + * @vcpus and @providers are optional and can be NULL.
> + *
> + * Queries for the @target based statistics.
> + * Returns a GPtrArray of GHashTables containing the statistics on success or
> + * NULL on failure.
> + */
> +
> +GPtrArray *
> +qemuMonitorJSONQueryStats(qemuMonitor *mon,
> +                          qemuMonitorQueryStatsTargetType target,
> +                          char **vcpus,
> +                          GPtrArray *providers)
> +{
> +    g_autoptr(virJSONValue) cmd = NULL;
> +    g_autoptr(virJSONValue) reply = NULL;
> +    g_autoptr(virJSONValue) vcpu_list = NULL;
> +    g_autoptr(virJSONValue) provider_list = NULL;
> +    virJSONValue *rv = NULL;
> +
> +    size_t i;
> +
> +    if (providers) {
> +        provider_list = virJSONValueNewArray();
> +
> +        for (i = 0; i < providers->len; i++) {
> +            g_autoptr(virJSONValue) provider_obj = virJSONValueNewObject();
> +            qemuMonitorQueryStatsProvider *provider = providers->pdata[i];
> +            const char *type_str = qemuMonitorQueryStatsProviderTypeToString(provider->provider);
> +            virBitmap *names = provider->names;
> +            int rc;
> +
> +            rc = virJSONValueObjectAppendString(provider_obj, "provider", type_str);
> +
> +            if (rc < 0)
> +                return NULL;
> +
> +            if (names) {
> +                g_autoptr(virJSONValue) provider_names = virJSONValueNewArray();
> +                int curBit = virBitmapNextSetBit(names, -1);
> +
> +                while (curBit >= 0) {
> +                    const char *name = qemuMonitorQueryStatsNameTypeToString(curBit);
> +
> +                    if (virJSONValueArrayAppendString(provider_names, name) < 0)
> +                        return NULL;
> +
> +                    curBit = virBitmapNextSetBit(names, curBit);
> +                }

Also this can be shorter with:

int curBit = -1;

while ((curBit = virBitmapNextSetBit(names, curBit)) != -1) {
   ...
}

Attachment: signature.asc
Description: PGP signature