[PATCH v2 9/9] hw/9pfs/9p.c: benchmark time on T_readdir request

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

This patch is not intended to be merged, it measures
and prints the time the 9p server spends on handling
a T_readdir request. It prints the total time it spent
on handling the request, and also the time it spent
on I/O (fs driver) only.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
---
 hw/9pfs/9p.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index a7d36b6350..c6f70b96ee 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -2299,6 +2299,15 @@ static void v9fs_free_dirents(struct V9fsDirEnt *e)
     }
 }
 
+static double wall_time(void)
+{
+    struct timeval t;
+    struct timezone tz;
+    gettimeofday(&t, &tz);
+    return t.tv_sec + t.tv_usec * 0.000001;
+}
+
+
 static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
                                         int32_t max_count)
 {
@@ -2318,6 +2327,8 @@ static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
      */
     const bool dostat = pdu->s->ctx.export_flags & V9FS_REMAP_INODES;
 
+    const double start = wall_time();
+
     /*
      * Fetch all required directory entries altogether on a background IO
      * thread from fs driver. We don't want to do that for each entry
@@ -2332,6 +2343,10 @@ static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
     }
     count = 0;
 
+    const double end = wall_time();
+    printf("\n\nTime 9p server spent on synth_readdir() I/O only (synth "
+           "driver): %fs\n", end - start);
+
     for (struct V9fsDirEnt *e = entries; e; e = e->next) {
         dent = e->dent;
 
@@ -2404,6 +2419,8 @@ static void coroutine_fn v9fs_readdir(void *opaque)
     V9fsPDU *pdu = opaque;
     V9fsState *s = pdu->s;
 
+    const double start = wall_time();
+
     retval = pdu_unmarshal(pdu, offset, "dqd", &fid,
                            &initial_offset, &max_count);
     if (retval < 0) {
@@ -2447,6 +2464,10 @@ out:
     put_fid(pdu, fidp);
 out_nofid:
     pdu_complete(pdu, retval);
+
+    const double end = wall_time();
+    printf("Time 9p server spent on entire T_readdir request: %fs "
+           "[IMPORTANT]\n", end - start);
 }
 
 static int v9fs_xattr_write(V9fsState *s, V9fsPDU *pdu, V9fsFidState *fidp,
-- 
2.20.1