util: Introduce monitor capability interface

This patch introduces the resource monitor and creates the interface
for getting host capability of resource monitor from the system resource
control file system.

The resource monitor takes the role of RDT monitoring group and could be
used to monitor the resource consumption information, such as the last
level cache occupancy and the utilization of memory bandwidth.

Signed-off-by: Wang Huaqiang <huaqiang.wang@intel.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

src/util/virresctrl.c

@@ -83,6 +83,9 @@ typedef virResctrlInfoPerLevel *virResctrlInfoPerLevelPtr;
 typedef struct _virResctrlInfoMemBW virResctrlInfoMemBW;
 typedef virResctrlInfoMemBW *virResctrlInfoMemBWPtr;
 
+typedef struct _virResctrlInfoMongrp virResctrlInfoMongrp;
+typedef virResctrlInfoMongrp *virResctrlInfoMongrpPtr;
+
 typedef struct _virResctrlAllocPerType virResctrlAllocPerType;
 typedef virResctrlAllocPerType *virResctrlAllocPerTypePtr;
 
@@ -139,6 +142,28 @@ struct _virResctrlInfoMemBW {
     unsigned int max_id;
 };
 
+struct _virResctrlInfoMongrp {
+    /* Maximum number of simultaneous monitors */
+    unsigned int max_monitor;
+    /* null-terminal string list for monitor features */
+    char **features;
+    /* Number of monitor features */
+    size_t nfeatures;
+
+    /* Last level cache related information */
+
+    /* This adjustable value affects the final reuse of resources used by
+     * monitor. After the action of removing a monitor, the kernel may not
+     * release all hardware resources that monitor used immediately if the
+     * cache occupancy value associated with 'removed' monitor is above this
+     * threshold. Once the cache occupancy is below this threshold, the
+     * underlying hardware resource will be reclaimed and be put into the
+     * resource pool for next reusing.*/
+    unsigned int cache_reuse_threshold;
+    /* The cache 'level' that has the monitor capability */
+    unsigned int cache_level;
+};
+
 struct _virResctrlInfo {
     virObject parent;
 
@@ -146,6 +171,8 @@ struct _virResctrlInfo {
     size_t nlevels;
 
     virResctrlInfoMemBWPtr membw_info;
+
+    virResctrlInfoMongrpPtr monitor_info;
 };
 
 
@@ -171,8 +198,12 @@ virResctrlInfoDispose(void *obj)
         VIR_FREE(level);
     }
 
+    if (resctrl->monitor_info)
+        virStringListFree(resctrl->monitor_info->features);
+
     VIR_FREE(resctrl->membw_info);
     VIR_FREE(resctrl->levels);
+    VIR_FREE(resctrl->monitor_info);
 }
 
 
@@ -555,6 +586,94 @@ virResctrlGetMemoryBandwidthInfo(virResctrlInfoPtr resctrl)
 }
 
 
+/*
+ * Retrieve monitor capability from the resource control file system.
+ *
+ * The monitor capability is exposed through "SYSFS_RESCTRL_PATH/info/L3_MON"
+ * directory under the resource control file system. The monitor capability is
+ * parsed by reading the interface files and stored in the structure
+ * 'virResctrlInfoMongrp'.
+ *
+ * Not all host supports the resource monitor, leave the pointer
+ * @resctrl->monitor_info empty if not supported.
+ */
+static int
+virResctrlGetMonitorInfo(virResctrlInfoPtr resctrl)
+{
+    int ret = -1;
+    int rv = -1;
+    char *featurestr = NULL;
+    char **features = NULL;
+    size_t nfeatures = 0;
+    virResctrlInfoMongrpPtr info_monitor = NULL;
+
+    if (VIR_ALLOC(info_monitor) < 0)
+        return -1;
+
+    /* For now, monitor only exists in level 3 cache */
+    info_monitor->cache_level = 3;
+
+    rv = virFileReadValueUint(&info_monitor->max_monitor,
+                              SYSFS_RESCTRL_PATH "/info/L3_MON/num_rmids");
+    if (rv == -2) {
+        /* The file doesn't exist, so it's unusable for us, probably resource
+         * monitor unsupported */
+        VIR_INFO("The file '" SYSFS_RESCTRL_PATH "/info/L3_MON/num_rmids' "
+                 "does not exist");
+        ret = 0;
+        virResetLastError();
+        goto cleanup;
+    } else if (rv < 0) {
+        /* Other failures are fatal, so just quit */
+        goto cleanup;
+    }
+
+    rv = virFileReadValueUint(&info_monitor->cache_reuse_threshold,
+                              SYSFS_RESCTRL_PATH
+                              "/info/L3_MON/max_threshold_occupancy");
+    if (rv == -2) {
+        /* If CMT is not supported, then 'max_threshold_occupancy' file
+         * will not exist. */
+        VIR_DEBUG("File '" SYSFS_RESCTRL_PATH
+                  "/info/L3_MON/max_threshold_occupancy' does not exist");
+        virResetLastError();
+    } else if (rv < 0) {
+        goto cleanup;
+    }
+
+    rv = virFileReadValueString(&featurestr,
+                                SYSFS_RESCTRL_PATH
+                                "/info/L3_MON/mon_features");
+    if (rv == -2)
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Cannot get mon_features from resctrl"));
+    if (rv < 0)
+        goto cleanup;
+
+    if (!*featurestr) {
+        /* If no feature found in "/info/L3_MON/mon_features",
+         * some error happens */
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Get empty feature list from resctrl"));
+        goto cleanup;
+    }
+
+    features = virStringSplitCount(featurestr, "\n", 0, &nfeatures);
+    VIR_DEBUG("Resctrl supported %ld monitoring features", nfeatures);
+
+    info_monitor->nfeatures = nfeatures;
+    VIR_STEAL_PTR(info_monitor->features, features);
+    VIR_STEAL_PTR(resctrl->monitor_info, info_monitor);
+
+    ret = 0;
+ cleanup:
+    VIR_FREE(featurestr);
+    virStringListFree(features);
+    VIR_FREE(info_monitor);
+    return ret;
+}
+
+
 static int
 virResctrlGetInfo(virResctrlInfoPtr resctrl)
 {
@@ -573,6 +692,10 @@ virResctrlGetInfo(virResctrlInfoPtr resctrl)
     if (ret < 0)
         goto cleanup;
 
+    ret = virResctrlGetMonitorInfo(resctrl);
+    if (ret < 0)
+        goto cleanup;
+
     ret = 0;
  cleanup:
     VIR_DIR_CLOSE(dirp);
@@ -613,6 +736,9 @@ virResctrlInfoIsEmpty(virResctrlInfoPtr resctrl)
     if (resctrl->membw_info)
         return false;
 
+    if (resctrl->monitor_info)
+        return false;
+
     for (i = 0; i < resctrl->nlevels; i++) {
         virResctrlInfoPerLevelPtr i_level = resctrl->levels[i];