[PATCH] shared/006: improve the speed of case running

[Zorro Lang <zlang@redhat.com>]

There're three problems of this case:
1. Thousands of threads will be created to create lots of files, then
   kernel need to waste lots of system resource to schedule these
   threads. Some poor performance machines will take long long time
   on that.
2. Per thread try to create 1000 files by run 1000 times "echo >file".

For the 1st problem, I limit 2 threads per cpu, and the maximum is 20.
For the 2nd problem, use "sed 1 1000 | xargs touch" to instead of
the old way.

With this change, this case can run over in 2 mins on my x86_64
virtual machine with 1 cpu and 1G memory. Before that, it was still
running even a quarter passed.

Signed-off-by: Zorro Lang <zlang@redhat.com>
---

Hi,

The performance of this case affect the test time of xfstests,
especially on poor performance VM. I always doubt it hangs there,
because it has run too long time.

After this improvement:
It ran 105s on my virtual machine with 1 cpu and 1G memory.
It ran 60s on my real machine with 8 cpu and 64G memory.

The difference of "for ((i=0;i<1000;i++)); echo -n > file$i;done"
and "touch file{1..1000}" is:
The 1st one will run 1000 times execve, open, close and so on. The
execve() will take much time, especially on VM.
But the 2nd one will run once execve, 1000 times open and once close.
open() take much less time than execve().

Too many threads really waste too much time. For example, on my VM,
when I use $((ncpus * 2)) threads to run this case, it ran 100s. But
if I use $((ncpus * 4)) threads, the time increase to 130s. So too
many threads is not helpful, in contrast it wastes more time.

Thanks,
Zorro

 tests/shared/006 | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/tests/shared/006 b/tests/shared/006
index 6a237c9..42cd34d 100755
--- a/tests/shared/006
+++ b/tests/shared/006
@@ -43,13 +43,16 @@ create_file()
 {
 	local dir=$1
 	local nr_file=$2
-	local prefix=$3
-	local i=0
 
-	while [ $i -lt $nr_file ]; do
-		echo -n > $dir/${prefix}_${i}
-		let i=$i+1
-	done
+	if [ ! -d $dir ]; then
+		mkdir -p $dir
+	fi
+
+	if [ ${nr_file} -gt 0 ]; then
+		pushd $dir >/dev/null
+		seq 1 $nr_file | xargs touch
+		popd >/dev/null
+	fi
 }
 
 # get standard environment, filters and checks
@@ -61,6 +64,9 @@ _supported_fs ext4 ext3 ext2 xfs
 _supported_os Linux
 
 _require_scratch
+_require_test_program "feature"
+
+ncpus=`$here/src/feature -o`
 
 rm -f $seqres.full
 echo "Silence is golden"
@@ -68,19 +74,27 @@ echo "Silence is golden"
 _scratch_mkfs_sized $((1024 * 1024 * 1024)) >>$seqres.full 2>&1
 _scratch_mount
 
-i=0
 free_inode=`_get_free_inode $SCRATCH_MNT`
 file_per_dir=1000
-loop=$((free_inode / file_per_dir + 1))
-mkdir -p $SCRATCH_MNT/testdir
-
-echo "Create $((loop * file_per_dir)) files in $SCRATCH_MNT/testdir" >>$seqres.full
-while [ $i -lt $loop ]; do
-	create_file $SCRATCH_MNT/testdir $file_per_dir $i >>$seqres.full 2>&1 &
-	let i=$i+1
+num_dirs=$(( free_inode / (file_per_dir + 1) ))
+num_threads=$(( ncpus * 2 ))
+[ $num_threads -gt 20 ] && num_threads=20
+loop=$(( num_dirs / num_threads ))
+
+echo "Create $((loop * num_threads)) dirs and $file_per_dir files per dir in $SCRATCH_MNT" >>$seqres.full
+for ((i=0; i<ncpus*2; i++)); do
+	for ((j=0; j<$loop; j++)); do
+		create_file $SCRATCH_MNT/testdir_$i_$j $file_per_dir
+	done &
 done
 wait
 
+free_inode=`_get_free_inode $SCRATCH_MNT`
+if [ $free_inode -gt 0 ]; then
+	echo "Create $((free_inode - 1)) files and 1 dir to fill all remaining free inodes" >>$seqres.full
+	create_file $SCRATCH_MNT/testdir_$i_$j $((free_inode - 1))
+fi
+
 # log inode status in $seqres.full for debug purpose
 echo "Inode status after taking all inodes" >>$seqres.full
 $DF_PROG -i $SCRATCH_MNT >>$seqres.full
-- 
2.7.4