perf tests: Fix test 68 zstd compression for s390

Commit 5aa9887 ("s390/cpum_sf: prohibit callchain data collection")
prohibits call graph sampling for hardware events on s390. The
information recorded is out of context and does not match.

On s390 this commit now breaks test case 68 Zstd perf.data
compression/decompression.

Therefore omit call graph sampling on s390 in this test.

Output before:
  [root@t35lp46 perf]# ./perf test -Fv 68
  68: Zstd perf.data compression/decompression              :
  --- start ---
  Collecting compressed record file:
  Error:
  cycles: PMU Hardware doesn't support sampling/overflow-interrupts.
                                Try 'perf stat'
  ---- end ----
  Zstd perf.data compression/decompression: FAILED!
  [root@t35lp46 perf]#

Output after:
[root@t35lp46 perf]# ./perf test -Fv 68
  68: Zstd perf.data compression/decompression              :
  --- start ---
  Collecting compressed record file:
  500+0 records in
  500+0 records out
  256000 bytes (256 kB, 250 KiB) copied, 0.00615638 s, 41.6 MB/s
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.004 MB /tmp/perf.data.X3M,
                        compressed (original 0.002 MB, ratio is 3.609) ]
  Checking compressed events stats:
  # compressed : Zstd, level = 1, ratio = 4
        COMPRESSED events:          1
  2ELIFREPh---- end ----
  Zstd perf.data compression/decompression: Ok
  [root@t35lp46 perf]#

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20200729135314.91281-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/record+zstd_comp_decomp.sh

@@ -12,7 +12,8 @@ skip_if_no_z_record() {
 
 collect_z_record() {
 	echo "Collecting compressed record file:"
-	$perf_tool record -o $trace_file -g -z -F 5000 -- \
+	[[ "$(uname -m)" != s390x ]] && gflag='-g'
+	$perf_tool record -o $trace_file $gflag -z -F 5000 -- \
 		dd count=500 if=/dev/urandom of=/dev/null
 }