[PATCH v2 2/7] 9pfs: Twalk benchmark

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

This patch is not intentended to be merged, it just acts as performance
A/B comparison benchmark for the subsequent patches.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
---
 tests/qtest/virtio-9p-test.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c
index 41fed41de1..2cd9e427b4 100644
--- a/tests/qtest/virtio-9p-test.c
+++ b/tests/qtest/virtio-9p-test.c
@@ -20,6 +20,18 @@
 #include "libqos/virtio-9p.h"
 #include "libqos/qgraph.h"
 
+/*
+ * to benchmark the real time (not CPU time) that elapsed between start of
+ * a request and arrival of its response
+ */
+static double wall_time(void)
+{
+    struct timeval t;
+    struct timezone tz;
+    gettimeofday(&t, &tz);
+    return t.tv_sec + t.tv_usec * 0.000001;
+}
+
 #define QVIRTIO_9P_TIMEOUT_US (10 * 1000 * 1000)
 static QGuestAllocator *alloc;
 
@@ -646,12 +658,30 @@ static void fs_walk(void *obj, void *data, QGuestAllocator *t_alloc)
     }
 
     do_attach(v9p);
+    const double start = wall_time();
     req = v9fs_twalk(v9p, 0, 1, P9_MAXWELEM, wnames, 0);
+    const double twalk = wall_time();
     v9fs_req_wait_for_reply(req, NULL);
+    const double waitforreply = wall_time();
     v9fs_rwalk(req, &nwqid, &wqid);
+    const double end = wall_time();
 
     g_assert_cmpint(nwqid, ==, P9_MAXWELEM);
 
+    printf("\nTime client spent on sending Twalk: %fs\n\n",
+           twalk - start);
+
+    printf("Time client spent for waiting for reply from server: %fs "
+           "[MOST IMPORTANT]\n", waitforreply - start);
+    printf("(This is the most important value, because it reflects the time\n"
+           "the 9p server required to process and return the result of the\n"
+           "Twalk request.)\n\n");
+
+    printf("Total client time: %fs\n", end - start);
+
+    //printf("Details of response message data: R_readddir nentries=%d "
+    //       "rbytes=%d\n", nentries, count);
+
     for (i = 0; i < P9_MAXWELEM; i++) {
         g_free(wnames[i]);
     }
-- 
2.20.1