[PATCH] fio: add full explanation of the output of fio

diff --git a/README.fio b/README.fio
index c93a22db057c36a81743dc763236ac3f4059763d..66022aa3d874e07a839bc9c0544dcd1ac1313f23 100644 (file)
--- a/README.fio
+++ b/README.fio
@@ -106,3 +106,89 @@ subsequent jobs.
 
 Also see the examples/ dir for sample job files.
 
+
+Interpreting the output
+-----------------------
+
+fio spits out a lot of output. While running, fio will display the
+status of the jobs created. An example of that would be:
+
+Threads now running: 2 : [ww] [5.73% done]
+
+The characters inside the square brackets denote the current status of
+each thread. The possible values (in typical life cycle order) are:
+
+P              Thread setup, but not started.
+C              Thread created and running, but not doing anything yet
+       R       Running, doing sequential reads.
+       r       Running, doing random reads.
+       W       Running, doing sequential writes.
+       w       Running, doing random writes.
+V              Running, doing verification of written data.
+E              Thread exited, not reaped by main thread yet.
+_              Thread reaped.
+
+The other values are fairly self explanatory - number of thread currently
+running and doing io, and the estimated completion percentage.
+
+When fio is done (or interrupted by ctrl-c), it will show the data for
+each thread, group of threads, and disks in that order. For each data
+direction, the output looks like:
+
+Client1 (g=0): err= 0:
+  write: io=    32MiB, bw=   666KiB/s, runt= 50320msec
+    slat (msec): min=    0, max=  136, avg= 0.03, dev= 1.92
+    clat (msec): min=    0, max=  631, avg=48.50, dev=86.82
+    bw (KiB/s) : min=    0, max= 1196, per=51.00%, avg=664.02, dev=681.68
+  cpu        : usr=1.49%, sys=0.25%, ctx=7969
+
+The client number is printed, along with the group id and error of that
+thread. Below is the io statistics, here for writes. In the order listed,
+they denote:
+
+io=            Number of megabytes io performed
+bw=            Average bandwidth rate
+runt=          The runtime of that thread
+       slat=   Submission latency (avg being the average, dev being the
+               standard deviation). This is the time it took to submit
+               the io.
+       clat=   Completion latency. Same names as slat, this denotes the
+               time from submission to completion of the io pieces.
+       bw=     Bandwidth. Same names as the xlat stats, but also includes
+               an approximate percentage of total aggregate bandwidth
+               this thread received in this group. This last value is
+               only really useful if the threads in this group are on the
+               same disk, since they are then competing for disk access.
+cpu=           CPU usage. User and system time, along with the number
+               of context switches this thread went through.
+
+After each client has been listed, the group statistics are printed. They
+will look like this:
+
+Run status group 0 (all jobs):
+   READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
+  WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
+
+For each data direction, it prints:
+
+io=            Number of megabytes io performed.
+aggrb=         Aggregate bandwidth of threads in this group.
+minb=          The minimum average bandwidth a thread saw.
+maxb=          The maximum average bandwidth a thread saw.
+mint=          The minimum runtime of a thread.
+maxt=          The maximum runtime of a thread.
+
+And finally, the disk statistics are printed. They will look like this:
+
+Disk stats (read/write):
+  sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
+
+Each value is printed for both reads and writes, with reads first. The
+numbers denote:
+
+ios=           Number of ios performed by all groups.
+merge=         Number of merges io the io scheduler.
+ticks=         Number of ticks we kept the disk busy.
+io_queue=      Total time spent in the disk queue.
+util=          The disk utilization. A value of 100% means we kept the disk
+               busy constantly, 50% would be a disk idling half of the time.

diff --git a/fio.c b/fio.c
index 5f7d53da0ed0e5a38f6305c9e60093ba456ed4ed..89f8e92371eddb27fe9dcca339b245f7c2b8e438 100644 (file)
--- a/fio.c
+++ b/fio.c
@@ -1797,7 +1797,7 @@ static void show_thread_status(struct thread_data *td,
        if (!(td->io_bytes[0] + td->io_bytes[1]) && !td->error)
                return;
 
-       printf("Client%d (g=%d): err=%2d:\n", td->thread_number, td->groupid, td->error);
+       printf("Client%d (groupid=%d): err=%2d:\n", td->thread_number, td->groupid, td->error);
 
        show_ddir_status(td, rs, td->ddir);
        show_ddir_status(td, rs, td->ddir ^ 1);
@@ -2145,6 +2145,11 @@ static void show_run_stats(void)
                        rs->agg[1] = (rs->io_mb[1]*1024*1000) / rs->max_run[1];
        }
 
+       /*
+        * don't overwrite last signal output
+        */
+       printf("\n");
+
        for (i = 0; i < thread_number; i++) {
                td = &threads[i];
                rs = &runstats[td->groupid];