[LTP] [PATCH] ksm: wait 3 increments of full_scans before checking the results

[Han Pingtian <phan@redhat.com>]

The KSM developer tell us that we should wait 3~5 increments of the
/sys/kernel/mm/ksm/full_scans before checking ksm* testcases's results.
Otherwise, there may be some stuck pages that cause the testing failed.

Signed-off-by: Han Pingtian <phan@redhat.com>
---
 testcases/kernel/mem/lib/mem.c |   27 +++++++++++++++++++++++++--
 1 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/mem/lib/mem.c b/testcases/kernel/mem/lib/mem.c
index 1a53359..98cca12 100644
--- a/testcases/kernel/mem/lib/mem.c
+++ b/testcases/kernel/mem/lib/mem.c
@@ -298,8 +298,31 @@ void group_check(int run, int pages_shared, int pages_sharing,
 		int pages_volatile, int pages_unshared,
 		int sleep_millisecs, int pages_to_scan)
 {
-        /* 5 seconds for ksm to scan pages. */
-	sleep(5);
+	int fd;
+	char buf[BUFSIZ];
+	int old_num, new_num;
+
+	fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
+	if (fd < 0)
+		tst_brkm(TBROK|TERRNO, cleanup, "open");
+
+        /* 1 seconds for ksm to scan pages. */
+	sleep(1);
+
+	/* wait 3 increments of full_scans */
+	if (read(fd, buf, BUFSIZ) < 0)
+		tst_brkm(TBROK|TERRNO, cleanup, "read");
+	old_num = new_num = atoi(buf);
+	lseek(fd, 0, SEEK_SET);
+	while (new_num < old_num * 3) {
+		sleep(1);
+		if (read(fd, buf, BUFSIZ) < 0)
+			tst_brkm(TBROK|TERRNO, cleanup, "read");
+		new_num = atoi(buf);
+		lseek(fd, 0, SEEK_SET);
+	}
+	close(fd);
+
 	tst_resm(TINFO, "check!");
 	check("run", run);
 	check("pages_shared", pages_shared);
-- 
1.7.1

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