qga: add command 'guest-get-cpustats'

A vCPU thread always reaches 100% utilization when:
- guest uses idle=poll
- disable HLT vm-exit
- enable MWAIT

Add new guest agent command 'guest-get-cpustats' to get guest CPU
statistics, we can know the guest workload and how busy the CPU is.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Message-Id: <20220707005602.696557-3-pizhenwei@bytedance.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

qga/commands-posix.c

@@ -2893,6 +2893,90 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error **errp)
     return guest_get_diskstats(errp);
 }
 
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    GuestCpuStatsList *head = NULL, **tail = &head;
+    const char *cpustats = "/proc/stat";
+    int clk_tck = sysconf(_SC_CLK_TCK);
+    FILE *fp;
+    size_t n;
+    char *line = NULL;
+
+    fp = fopen(cpustats, "r");
+    if (fp  == NULL) {
+        error_setg_errno(errp, errno, "open(\"%s\")", cpustats);
+        return NULL;
+    }
+
+    while (getline(&line, &n, fp) != -1) {
+        GuestCpuStats *cpustat = NULL;
+        GuestLinuxCpuStats *linuxcpustat;
+        int i;
+        unsigned long user, system, idle, iowait, irq, softirq, steal, guest;
+        unsigned long nice, guest_nice;
+        char name[64];
+
+        i = sscanf(line, "%s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
+                   name, &user, &nice, &system, &idle, &iowait, &irq, &softirq,
+                   &steal, &guest, &guest_nice);
+
+        /* drop "cpu 1 2 3 ...", get "cpuX 1 2 3 ..." only */
+        if ((i == EOF) || strncmp(name, "cpu", 3) || (name[3] == '\0')) {
+            continue;
+        }
+
+        if (i < 5) {
+            slog("Parsing cpu stat from %s failed, see \"man proc\"", cpustats);
+            break;
+        }
+
+        cpustat = g_new0(GuestCpuStats, 1);
+        cpustat->type = GUEST_CPU_STATS_TYPE_LINUX;
+
+        linuxcpustat = &cpustat->u.q_linux;
+        linuxcpustat->cpu = atoi(&name[3]);
+        linuxcpustat->user = user * 1000 / clk_tck;
+        linuxcpustat->nice = nice * 1000 / clk_tck;
+        linuxcpustat->system = system * 1000 / clk_tck;
+        linuxcpustat->idle = idle * 1000 / clk_tck;
+
+        if (i > 5) {
+            linuxcpustat->has_iowait = true;
+            linuxcpustat->iowait = iowait * 1000 / clk_tck;
+        }
+
+        if (i > 6) {
+            linuxcpustat->has_irq = true;
+            linuxcpustat->irq = irq * 1000 / clk_tck;
+            linuxcpustat->has_softirq = true;
+            linuxcpustat->softirq = softirq * 1000 / clk_tck;
+        }
+
+        if (i > 8) {
+            linuxcpustat->has_steal = true;
+            linuxcpustat->steal = steal * 1000 / clk_tck;
+        }
+
+        if (i > 9) {
+            linuxcpustat->has_guest = true;
+            linuxcpustat->guest = guest * 1000 / clk_tck;
+        }
+
+        if (i > 10) {
+            linuxcpustat->has_guest = true;
+            linuxcpustat->guest = guest * 1000 / clk_tck;
+            linuxcpustat->has_guestnice = true;
+            linuxcpustat->guestnice = guest_nice * 1000 / clk_tck;
+        }
+
+        QAPI_LIST_APPEND(tail, cpustat);
+    }
+
+    free(line);
+    fclose(fp);
+    return head;
+}
+
 #else /* defined(__linux__) */
 
 void qmp_guest_suspend_disk(Error **errp)
@@ -3247,6 +3331,11 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error **errp)
     return NULL;
 }
 
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
 
 #endif /* CONFIG_FSFREEZE */
 

qga/commands-win32.c

@@ -2543,3 +2543,9 @@ GuestDiskStatsInfoList *qmp_guest_get_diskstats(Error **errp)
     error_setg(errp, QERR_UNSUPPORTED);
     return NULL;
 }
+
+GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}

qga/qapi-schema.json

@@ -1576,3 +1576,84 @@
 { 'command': 'guest-get-diskstats',
   'returns': ['GuestDiskStatsInfo']
 }
+
+##
+# @GuestCpuStatsType:
+#
+# An enumeration of OS type
+#
+# Since: 7.1
+##
+{ 'enum': 'GuestCpuStatsType',
+  'data': [ 'linux' ] }
+
+
+##
+# @GuestLinuxCpuStats:
+#
+# CPU statistics of Linux
+#
+# @cpu: CPU index in guest OS
+#
+# @user: Time spent in user mode
+#
+# @nice: Time spent in user mode with low priority (nice)
+#
+# @system: Time spent in system mode
+#
+# @idle: Time spent in the idle task
+#
+# @iowait: Time waiting for I/O to complete (since Linux 2.5.41)
+#
+# @irq: Time servicing interrupts (since Linux 2.6.0-test4)
+#
+# @softirq: Time servicing softirqs (since Linux 2.6.0-test4)
+#
+# @steal: Stolen time by host (since Linux 2.6.11)
+#
+# @guest: ime spent running a virtual CPU for guest operating systems under
+#         the  control of the Linux kernel (since Linux 2.6.24)
+#
+# @guestnice: Time spent running a niced guest (since Linux 2.6.33)
+#
+# Since: 7.1
+##
+{ 'struct': 'GuestLinuxCpuStats',
+  'data': {'cpu': 'int',
+           'user': 'uint64',
+           'nice': 'uint64',
+           'system': 'uint64',
+           'idle': 'uint64',
+           '*iowait': 'uint64',
+           '*irq': 'uint64',
+           '*softirq': 'uint64',
+           '*steal': 'uint64',
+           '*guest': 'uint64',
+           '*guestnice': 'uint64'
+           } }
+
+##
+# @GuestCpuStats:
+#
+# Get statistics of each CPU in millisecond.
+#
+# - @linux: Linux style CPU statistics
+#
+# Since: 7.1
+##
+{ 'union': 'GuestCpuStats',
+  'base': { 'type': 'GuestCpuStatsType' },
+  'discriminator': 'type',
+  'data': { 'linux': 'GuestLinuxCpuStats' } }
+
+##
+# @guest-get-cpustats:
+#
+# Retrieve information about CPU stats.
+# Returns: List of CPU stats of guest.
+#
+# Since: 7.1
+##
+{ 'command': 'guest-get-cpustats',
+  'returns': ['GuestCpuStats']
+}