qga: implement a 'guest-get-load' command

Provide a way to report the process load average, via a new
'guest-get-load' command.

This is only implemented for POSIX platforms providing 'getloadavg'.

Example illustrated with qmp-shell:

(QEMU) guest-get-load
{
    "return": {
        "load15m": 1.546875,
        "load1m": 1.669921875,
        "load5m": 1.9306640625
    }
}

Windows has no native equivalent API, but it would be possible to
simulate it as illustrated here (BSD-3-Clause):

  https://github.com/giampaolo/psutil/pull/1485

This is left as an exercise for future contributors.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Message-ID: <20241202121927.864335-1-berrange@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 636307b..6e3c15f 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -1368,3 +1368,23 @@ char *qga_get_host_name(Error **errp)
 
     return g_steal_pointer(&hostname);
 }
+
+#ifdef CONFIG_GETLOADAVG
+GuestLoadAverage *qmp_guest_get_load(Error **errp)
+{
+    double loadavg[3];
+    GuestLoadAverage *ret = NULL;
+
+    if (getloadavg(loadavg, G_N_ELEMENTS(loadavg)) < 0) {
+        error_setg_errno(errp, errno,
+                         "cannot query load average");
+        return NULL;
+    }
+
+    ret = g_new0(GuestLoadAverage, 1);
+    ret->load1m = loadavg[0];
+    ret->load5m = loadavg[1];
+    ret->load15m = loadavg[2];
+    return ret;
+}
+#endif