genfio: Warn users if read occurs before write

The default mode was to generate read pattern _before_ the write ones.
On some storage device that handle read on untouch sectors by answering
zero from the cache, the result is totally invalid and cheat about the
real read capabilities of the device.

This patch does change the default mode to emit writes before reads.
It also add a warning message if user is setting up some modes by itself
and generate a read_before_write pattern.

That's only a warning message that last a few seconds but could avoid
running a wrong benchmark.

This commit occurs after a real case of invalid performances due to read
emitted to an untouched block volume.

Typical output will be:
 root@vm1-1: genfio -d vdb -s -b 4k,128k,4m -m read,randread
 ###############################################################
 # Warning : You are reading data while never wrote them before#
 # On some storage devices, this could lead to invalid results #
 #                                                             #
 # Press Ctrl-C to adjust pattern order if you have doubts     #
 # Or Wait 5 seconds before the file will be created           #
 ###############################################################
 Generating vm1-1-4k,128k,4m-sequential-read,randread-vdb.fio
 Estimated Time = 1800 seconds : 0 hour 30 minutes

diff --git a/tools/genfio b/tools/genfio
index 3599450663e83951dda78a1697e81b43f38678e8..123f6e42a6025fbff8f84483b0c5cb3a34524de5 100755 (executable)
--- a/tools/genfio
+++ b/tools/genfio
@@ -27,7 +27,7 @@ OUTFILE=
 DISKS=
 RUNTIME=300
 ETA=0
-MODES="read,write,randread,randwrite"
+MODES="write,randwrite,read,randread"
 SHORT_HOSTNAME=
 CACHED_IO="FALSE"
 PREFIX=""
@@ -58,7 +58,7 @@ show_help() {
                                        Separated each blocksize with a comma
                                        Default is 4k
 -m mode1,[mode2,mode3, ...]     : Define the fio IO profile to use like read, write, randread, randwrite
-                                       Default is "read,write,randread,randwrite"
+                                       Default is "write,randwrite,read,randread"
 -x prefix                      : Add a prefix to the fio filename
                                        Useful to let a context associated with the file
                                        If the prefix features a / (slash), prefix will be considered as a directory
@@ -68,20 +68,20 @@ Example:
 $PROG -d sdb,sdc,sdd,sde -a -b 4k,128k,1m -r 100 -a -x dellr720-day2/
 
        Will generate an fio file that will run
-               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 4k with read,write,randread,randwrite tests
+               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 4k with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 4 disks * 100 seconds
-               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 128k with read,write,randread,randwrite tests
+               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 128k with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 4 disks * 100 seconds
-               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 1m with read,write,randread,randwrite tests
+               - a sequential bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 1m with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 4 disks * 100 seconds
-               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 4k with read,write,randread,randwrite tests
+               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 4k with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 100 seconds
-               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 128k with read,write,randread,randwrite tests
+               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 128k with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 100 seconds
-               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 1m with read,write,randread,randwrite tests
+               - a parallel bench on /dev/sdb /dev/sdc /dev/sdd /dev/sde for block size = 1m with write,randwrite,read,randread tests
                        ETA ~ 4 tests * 100 seconds
 
-Generating dellr720-day2/localhost-4k,128k,1m-all-read,write,randread,randwrite-sdb,sdc,sdd,sde.fio
+Generating dellr720-day2/localhost-4k,128k,1m-all-write,randwrite,read,randread-sdb,sdc,sdd,sde.fio
 Estimated Time = 6000 seconds : 1 hour 40 minutes
 EOF
 }
@@ -260,9 +260,43 @@ fi
 
 }
 
+check_mode_order() {
+FOUND_WRITE="NO"
+CAUSE="You are reading data before writing them          "
+
+# If no write occurs, let's show a different message
+echo $MODES | grep -q "write"
+if [ "$?" -ne 0 ]; then
+       CAUSE="You are reading data while never wrote them before"
+fi
+
+for mode in $(echo $MODES | tr "," " "); do
+       echo $mode | grep -q write
+       if [ "$?" -eq 0 ]; then
+               FOUND_WRITE="YES"
+       fi
+       echo $mode | grep -q "read"
+       if [ "$?" -eq 0 ]; then
+               if [ "$FOUND_WRITE" = "NO" ]; then
+                       echo "###############################################################"
+                       echo "# Warning : $CAUSE#"
+                       echo "# On some storage devices, this could lead to invalid results #"
+                       echo "#                                                             #"
+                       echo "# Press Ctrl-C to adjust pattern order if you have doubts     #"
+                       echo "# Or Wait 5 seconds before the file will be created           #"
+                       echo "###############################################################"
+                       sleep 5
+                       # No need to try showing the message more than one time
+                       return
+               fi
+       fi
+done
+}
+
 
 ########## MAIN
 parse_cmdline $@
+check_mode_order
 gen_template
 
 echo "Generating $OUTFILE"