Add microsecs/op display to pg_test_fsync utility

e.g. fsync  2103.613 ops/sec (   475 microsecs/op)

Peter Geoghegan

diff --git a/contrib/pg_test_fsync/pg_test_fsync.c b/contrib/pg_test_fsync/pg_test_fsync.c
index 9fe2301e419a569d6f6111c606a22c01c2690c9a..7f7368a315660abbc36917fd11d5e7a1ccd48db5 100644 (file)
--- a/contrib/pg_test_fsync/pg_test_fsync.c
+++ b/contrib/pg_test_fsync/pg_test_fsync.c
@@ -25,7 +25,8 @@
 
 #define LABEL_FORMAT       "        %-32s"
 #define NA_FORMAT          "%18s"
-#define OPS_FORMAT         "%9.3f ops/sec"
+#define OPS_FORMAT         "%9.3f ops/sec (%6.f microsecs/op)"
+#define USECS_SEC          1000000
 
 /* These are macros to avoid timing the function call overhead. */
 #ifndef WIN32
@@ -568,8 +569,9 @@ print_elapse(struct timeval start_t, struct timeval stop_t, int ops)
    double      total_time = (stop_t.tv_sec - start_t.tv_sec) +
    (stop_t.tv_usec - start_t.tv_usec) * 0.000001;
    double      per_second = ops / total_time;
+   double      avg_op_time_us = (total_time / ops) * USECS_SEC;
 
-   printf(OPS_FORMAT "\n", per_second);
+   printf(OPS_FORMAT "\n", per_second, avg_op_time_us);
 }
 
 #ifndef WIN32

diff --git a/doc/src/sgml/pgtestfsync.sgml b/doc/src/sgml/pgtestfsync.sgml
index 95ba3b81e0c876d6c4970a1315b05fe0587b8408..00ef209fa2547b7e399bd1fb2db38b03b4c9dcea 100644 (file)
--- a/doc/src/sgml/pgtestfsync.sgml
+++ b/doc/src/sgml/pgtestfsync.sgml
@@ -30,11 +30,14 @@
   <application>pg_test_fsync</> is intended to give you a reasonable
   idea of what the fastest <xref linkend="guc-wal-sync-method"> is on your
   specific system,
-  as well as supplying diagnostic information in the event of an
-  identified I/O problem.  However, differences shown by <application>pg_test_fsync</application>
-  might not make any difference in real database throughput, especially
-  since many database servers are not speed-limited by their transaction
-  logs.
+  as well as supplying diagnostic information in the event of an identified I/O
+  problem.  However, differences shown by
+  <application>pg_test_fsync</application> might not make any significant
+  difference in real database throughput, especially since many database servers
+  are not speed-limited by their transaction logs.
+  <application>pg_test_fsync</application> reports average file sync operation
+  time in microseconds for each wal_sync_method, which can be used to inform
+  efforts to optimize the value of <varname>commit_delay</varname>.
  </para>
  </refsect1>