Sample the log traffic to work out its data rate so that we

have a better idea of predicting when it will get to the end
of the log. This way we can handle a change in log traffic in
the future. A test to keep an eye on log traffic is more of
a performance test than should be done elsewhere.
Merge of master-melb:xfs-cmds:31053a by kenmcd.

  Sample the log traffic to work out its data rate so that we
  have a better idea of predicting when it will get to the end
  of the log. This way we can handle a change in log traffic in
  the future.

016

@@ -50,7 +50,7 @@ _init()
     echo "*** reset partition"
     $here/src/devzero -b 2048 -n 50 -v 198 $SCRATCH_DEV
     echo "*** mkfs"
-    force_opts="-dsize=50m -lsize=2097152"
+    force_opts="-dsize=50m -lsize=$log_size"
     echo mkfs_xfs $force_opts $SCRATCH_DEV >>$seq.full
     _scratch_mkfs_xfs $force_opts >$tmp.mkfs0 2>&1
     [ $? -ne 0 ] && \
@@ -156,6 +156,10 @@ _supported_os Linux
 
 rm -f $seq.full
 
+# mkfs sizes
+log_size=2097152
+log_size_bb=`expr $log_size / 512`
+
 _require_scratch
 _init
 
@@ -163,27 +167,47 @@ block=`_after_log $SCRATCH_DEV`
 echo "fsblock after log = $block"               >>$seq.full
 _check_corrupt $SCRATCH_DEV $block
 
-size=`_log_size`
-echo "log size = $size BB"                      >>$seq.full
+actual_log_size=`_log_size`
+echo "log size = $actual_log_size BB"                      >>$seq.full
 head=`_log_head`
 echo "log position = $head"                     >>$seq.full
 lsunit=`_log_sunit`
 echo "log sunit = $lsunit"			>>$seq.full
 
-[ $size -eq 4096 ] || \
+# sanity checks
+[ $actual_log_size -eq $log_size_bb ] || \
     _fail "!!! unexpected log size $size"
 [ $head -eq 2 -o $head -eq $((lsunit/512)) ] || \
     _fail "!!! unexpected initial log position $head vs. $((lsunit/512))"
 
-echo "    lots of traffic"                      >>$seq.full
-_log_traffic 850
+# find how how many blocks per op for 100 ops
+# ignore the fact that it will also include an unmount record etc...
+# this should be small overall
+echo "    lots of traffic for sampling" >>$seq.full
+sample_size_ops=100
+_log_traffic $sample_size_ops
+head1=`_log_head`
+num_blocks=`expr $head1 - $head`
+blocks_per_op=`echo "scale=3; $num_blocks / $sample_size_ops" | bc`
+echo "blocks_per_op = $blocks_per_op" >>$seq.full
+num_expected_ops=`echo "$log_size_bb / $blocks_per_op" | bc`
+echo "num_expected_ops = $num_expected_ops" >>$seq.full
+num_expected_to_go=`echo "$num_expected_ops - $sample_size_ops" | bc`
+echo "num_expected_to_go = $num_expected_to_go" >>$seq.full
+
+echo "    lots more traffic" >>$seq.full
+_log_traffic $num_expected_to_go
 head=`_log_head`
 echo "log position = $head"                     >>$seq.full
 
-[ $head -gt 3850 -a $head -lt 4050 ] || \
-    _fail "!!! unexpected log position $head"
+# e.g. 3891
+near_end_min=`echo "0.95 * $log_size_bb" | bc | sed 's/\..*//'`
+echo "near_end_min = $near_end_min" >>$seq.full
 
-for c in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
+[ $head -gt $near_end_min -a $head -lt $log_size_bb ] || \
+    _fail "!!! unexpected near end log position $head"
+
+for c in `seq 0 20`
 do
     echo "   little traffic"            >>$seq.full
     _log_traffic 2
@@ -193,7 +217,7 @@ do
 done
 
 [ $head -lt 1000 ] || \
-    _fail "!!! unexpected log position $head"
+    _fail "!!! unexpected wrapped log position $head"
 
 # success, all done
 status=0

016.out

@@ -11,6 +11,10 @@ Wrote 51200.00Kb (value 0xc6)
    *** mount
    *** fiddle
    *** unmount
+*** generate log traffic
+   *** mount
+   *** fiddle
+   *** unmount
 *** check for corruption
 *** generate log traffic
    *** mount