selftests: mm: add KSM_MERGE_TIME tests

add KSM_MERGE_TIME and KSM_MERGE_TIME_HUGE_PAGES tests with size of 100.

./run_vmtests.sh -t ksm
-----------------------------
running ./ksm_tests -H -s 100
-----------------------------

Number of normal pages:    0
Number of huge pages:    50
Total size:    100 MiB
Total time:    0.399844662 s
Average speed:  250.097 MiB/s

[PASS]
-----------------------------
running ./ksm_tests -P -s 100
-----------------------------

Total size:    100 MiB
Total time:    0.451931496 s
Average speed:  221.272 MiB/s

[PASS]

---
v1 -> v2
collect Reviewed-by from David

 tools/testing/selftests/mm/run_vmtests.sh | 4 ++++
 1 file changed, 4 insertions(+)

index 3f26f6e15b2a..ca3738e042c2 100755
@@ -262,6 +262,10 @@ CATEGORY="madv_populate" run_test ./madv_populate
 
 CATEGORY="memfd_secret" run_test ./memfd_secret
 
+# KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100
+CATEGORY="ksm" run_test ./ksm_tests -H -s 100
+# KSM KSM_MERGE_TIME test with size of 100
+CATEGORY="ksm" run_test ./ksm_tests -P -s 100
 # KSM MADV_MERGEABLE test with 10 identical pages
 CATEGORY="ksm" run_test ./ksm_tests -M -p 10
 # KSM unmerge test

2.34.1