[PATCH v3 0/2] KSM: support smart-scan feature

[PATCH v3 0/2] KSM: support smart-scan feature

[Stefan Roesch]

This patch series makes two changes:
- Disable the smart-scan feature for ksm01 - ksm04
  This is necessary to make sure that the volatile metrics have the
  expected counts.
- Add a new test for the smart-scan feature
  The new test verifies that the smart-scan feature skips pages when it has
  been enabled for a VMA.

Versions:
- V3:
  - Disable smart scan for ksm05 and ksm06
  - add ksm07 to runtest/mm
  - change documentation format in header of ksm07.c
  - Move function create_memory_for_smartscan() to ksm07.c
  - Rename create_memory_for_smartscan() to create_memory()
  
- V2:
  - Disable smart_scan in the test setup structure
  - Remove the changes in create_same_memory()
  - Add the new testcase ksm07 for the smart scan test
  

Stefan Roesch (2):
  mem: disable KSM smart scan for ksm tests
  add ksm test for smart-scan feature

 runtest/mm                       |   1 +
 testcases/kernel/mem/.gitignore  |   1 +
 testcases/kernel/mem/ksm/ksm01.c |   2 +
 testcases/kernel/mem/ksm/ksm02.c |   2 +
 testcases/kernel/mem/ksm/ksm03.c |   2 +
 testcases/kernel/mem/ksm/ksm04.c |   2 +
 testcases/kernel/mem/ksm/ksm05.c |   2 +
 testcases/kernel/mem/ksm/ksm06.c |   2 +
 testcases/kernel/mem/ksm/ksm07.c | 131 +++++++++++++++++++++++++++++++
 9 files changed, 145 insertions(+)
 create mode 100644 testcases/kernel/mem/ksm/ksm07.c


base-commit: 8c89ef3d451087ed6e18750bd5eedd10e5ab3d2e
-- 
2.39.3

[PATCH v3 1/2] mem: disable KSM smart scan for ksm tests

[Stefan Roesch]

This disables the "smart scan" KSM feature to make sure that the volatile
count remains at 0.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
Reviewed-by: Petr Vorel <pvorel@suse.cz>

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202311161132.13d8ce5a-oliver.sang@intel.com
---
 testcases/kernel/mem/ksm/ksm01.c | 2 ++
 testcases/kernel/mem/ksm/ksm02.c | 2 ++
 testcases/kernel/mem/ksm/ksm03.c | 2 ++
 testcases/kernel/mem/ksm/ksm04.c | 2 ++
 testcases/kernel/mem/ksm/ksm05.c | 2 ++
 testcases/kernel/mem/ksm/ksm06.c | 2 ++
 6 files changed, 12 insertions(+)

diff --git a/testcases/kernel/mem/ksm/ksm01.c b/testcases/kernel/mem/ksm/ksm01.c
index bcd095865..e2d3d9e00 100644
--- a/testcases/kernel/mem/ksm/ksm01.c
+++ b/testcases/kernel/mem/ksm/ksm01.c
@@ -86,6 +86,8 @@ static struct tst_test test = {
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
 		{"/sys/kernel/mm/ksm/merge_across_nodes", "1",
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
diff --git a/testcases/kernel/mem/ksm/ksm02.c b/testcases/kernel/mem/ksm/ksm02.c
index bce639dce..3707de95d 100644
--- a/testcases/kernel/mem/ksm/ksm02.c
+++ b/testcases/kernel/mem/ksm/ksm02.c
@@ -107,6 +107,8 @@ static struct tst_test test = {
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
 		{"/sys/kernel/mm/ksm/merge_across_nodes", "1",
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
diff --git a/testcases/kernel/mem/ksm/ksm03.c b/testcases/kernel/mem/ksm/ksm03.c
index 4a733269f..cff74700d 100644
--- a/testcases/kernel/mem/ksm/ksm03.c
+++ b/testcases/kernel/mem/ksm/ksm03.c
@@ -89,6 +89,8 @@ static struct tst_test test = {
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
 		{"/sys/kernel/mm/ksm/merge_across_nodes", "1",
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
diff --git a/testcases/kernel/mem/ksm/ksm04.c b/testcases/kernel/mem/ksm/ksm04.c
index 4f1f2f721..9935e32d7 100644
--- a/testcases/kernel/mem/ksm/ksm04.c
+++ b/testcases/kernel/mem/ksm/ksm04.c
@@ -109,6 +109,8 @@ static struct tst_test test = {
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
 		{"/sys/kernel/mm/ksm/merge_across_nodes", "1",
 			TST_SR_SKIP_MISSING | TST_SR_TCONF_RO},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
diff --git a/testcases/kernel/mem/ksm/ksm05.c b/testcases/kernel/mem/ksm/ksm05.c
index 1f58c8325..61e740843 100644
--- a/testcases/kernel/mem/ksm/ksm05.c
+++ b/testcases/kernel/mem/ksm/ksm05.c
@@ -89,6 +89,8 @@ static struct tst_test test = {
 	.test_all = test_ksm,
 	.save_restore = (const struct tst_path_val[]) {
 		{"/sys/kernel/mm/ksm/run", "1", TST_SR_TBROK},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
diff --git a/testcases/kernel/mem/ksm/ksm06.c b/testcases/kernel/mem/ksm/ksm06.c
index 0b159e5c7..80fdf1e47 100644
--- a/testcases/kernel/mem/ksm/ksm06.c
+++ b/testcases/kernel/mem/ksm/ksm06.c
@@ -142,6 +142,8 @@ static struct tst_test test = {
 		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TBROK},
 		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TBROK},
 		{"/sys/kernel/mm/ksm/merge_across_nodes", NULL, TST_SR_TCONF},
+		{"/sys/kernel/mm/ksm/smart_scan", "0",
+			TST_SR_SKIP_MISSING | TST_SR_TBROK_RO},
 		{}
 	},
 	.needs_kconfigs = (const char *const[]){
-- 
2.39.3

[PATCH v3 2/2] add ksm test for smart-scan feature

[Stefan Roesch]

This adds a new ksm (kernel samepage merging) test to evaluate the new
smart scan feature. It allocates a page and fills it with 'a'
characters. It captures the pages_skipped counter, waits for a few
iterations and captures the pages_skipped counter again. The expectation
is that over 50% of the page scans are skipped (There is only one page
that has KSM enabled and it gets scanned during each iteration and it
cannot be de-duplicated).

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 runtest/mm                       |   1 +
 testcases/kernel/mem/.gitignore  |   1 +
 testcases/kernel/mem/ksm/ksm07.c | 131 +++++++++++++++++++++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 testcases/kernel/mem/ksm/ksm07.c

diff --git a/runtest/mm b/runtest/mm
index f288fed36..d859b331c 100644
--- a/runtest/mm
+++ b/runtest/mm
@@ -70,6 +70,7 @@ ksm05 ksm05 -I 10
 ksm06 ksm06
 ksm06_1 ksm06 -n 10
 ksm06_2 ksm06 -n 8000
+ksm07 ksm07
 
 cpuset01 cpuset01
 
diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
index 7258489ed..c96fe8bfc 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -53,6 +53,7 @@
 /ksm/ksm04
 /ksm/ksm05
 /ksm/ksm06
+/ksm/ksm07
 /mem/mem02
 /mmapstress/mmap-corruption01
 /mmapstress/mmapstress01
diff --git a/testcases/kernel/mem/ksm/ksm07.c b/testcases/kernel/mem/ksm/ksm07.c
new file mode 100644
index 000000000..16153fdb2
--- /dev/null
+++ b/testcases/kernel/mem/ksm/ksm07.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2010-2017  Red Hat, Inc.
+ */
+/*\
+ * [Description]
+ *
+ * Kernel Samepage Merging (KSM)
+ *
+ * This adds a new ksm (kernel samepage merging) test to evaluate the new
+ * smart scan feature. It allocates a page and fills it with 'a'
+ * characters. It captures the pages_skipped counter, waits for a few
+ * iterations and captures the pages_skipped counter again. The expectation
+ * is that over 50% of the page scans are skipped (There is only one page
+ * that has KSM enabled and it gets scanned during each iteration and it
+ * cannot be de-duplicated).
+ *
+ * Prerequisites:
+ *
+ * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
+ *    distrub the testing as they also change some ksm tunables depends
+ *    on current workloads.
+ */
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "../include/mem.h"
+#include "ksm_common.h"
+
+/* This test allocates one page, fills the page with a's, captures the
+ * full_scan and pages_skipped counters. Then it makes sure at least 3
+ * full scans have been performed and measures the above counters again.
+ * The expectation is that at least 50% of the pages are skipped.
+ *
+ * To wait for at least 3 scans it uses the wait_ksmd_full_scan() function. In
+ * reality, it will be a lot more scans as the wait_ksmd_full_scan() function
+ * sleeps for one second.
+ */
+static void create_memory(void)
+{
+	int status;
+	int full_scans_begin;
+	int full_scans_end;
+	int pages_skipped_begin;
+	int pages_skipped_end;
+	int diff_pages;
+	int diff_scans;
+	unsigned long page_size;
+	char *memory;
+
+	/* Apply for the space for memory. */
+	page_size = sysconf(_SC_PAGE_SIZE);
+	memory = SAFE_MALLOC(page_size);
+
+	for (int i = 0; i < 1; i++) {
+		memory = SAFE_MMAP(NULL, page_size, PROT_READ|PROT_WRITE,
+			MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+#ifdef HAVE_DECL_MADV_MERGEABLE
+		if (madvise(memory, page_size, MADV_MERGEABLE) == -1)
+			tst_brk(TBROK|TERRNO, "madvise");
+#endif
+	}
+	memset(memory, 'a', page_size);
+
+	tst_res(TINFO, "KSM merging...");
+	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
+		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
+	}
+
+	/* Set defalut ksm scan values. */
+	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
+	SAFE_FILE_PRINTF(PATH_KSM "pages_to_scan", "%ld", 100l);
+	SAFE_FILE_PRINTF(PATH_KSM "sleep_millisecs", "0");
+
+	/* Measure pages skipped aka "smart scan". */
+	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_begin);
+	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
+	wait_ksmd_full_scan();
+
+	tst_res(TINFO, "stop KSM.");
+	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
+
+	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
+	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_end);
+	diff_pages = pages_skipped_end - pages_skipped_begin;
+	diff_scans = full_scans_end - full_scans_begin;
+
+	if (diff_pages < diff_scans * 50 / 100) {
+		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
+	} else {
+		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
+	}
+
+	while (waitpid(-1, &status, 0) > 0)
+		if (WEXITSTATUS(status) != 0)
+			tst_res(TFAIL, "child exit status is %d",
+					WEXITSTATUS(status));
+}
+
+static void verify_ksm(void)
+{
+	create_memory();
+}
+
+static struct tst_test test = {
+	.needs_root = 1,
+	.forks_child = 1,
+	.options = (struct tst_option[]) {
+		{}
+	},
+	.save_restore = (const struct tst_path_val[]) {
+		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
+		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
+		{"/sys/kernel/mm/ksm/smart_scan", "1",
+			TST_SR_SKIP_MISSING | TST_SR_TCONF},
+		{}
+	},
+	.needs_kconfigs = (const char *const[]){
+		"CONFIG_KSM=y",
+		NULL
+	},
+	.test_all = verify_ksm,
+};
-- 
2.39.3

Re: [LTP] [PATCH v3 2/2] add ksm test for smart-scan feature

[Cyril Hrubis]

Hi!
> diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
> index 7258489ed..c96fe8bfc 100644
> --- a/testcases/kernel/mem/.gitignore
> +++ b/testcases/kernel/mem/.gitignore
> @@ -53,6 +53,7 @@
>  /ksm/ksm04
>  /ksm/ksm05
>  /ksm/ksm06
> +/ksm/ksm07
>  /mem/mem02
>  /mmapstress/mmap-corruption01
>  /mmapstress/mmapstress01
> diff --git a/testcases/kernel/mem/ksm/ksm07.c b/testcases/kernel/mem/ksm/ksm07.c
> new file mode 100644
> index 000000000..16153fdb2
> --- /dev/null
> +++ b/testcases/kernel/mem/ksm/ksm07.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2010-2017  Red Hat, Inc.
                      ^
		      2023?
> + */
> +/*\
> + * [Description]
> + *
> + * Kernel Samepage Merging (KSM)
> + *
> + * This adds a new ksm (kernel samepage merging) test to evaluate the new
> + * smart scan feature. It allocates a page and fills it with 'a'
> + * characters. It captures the pages_skipped counter, waits for a few
> + * iterations and captures the pages_skipped counter again. The expectation
> + * is that over 50% of the page scans are skipped (There is only one page
> + * that has KSM enabled and it gets scanned during each iteration and it
> + * cannot be de-duplicated).
> + *
> + * Prerequisites:
> + *
> + * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
> + *    distrub the testing as they also change some ksm tunables depends
> + *    on current workloads.

I guess that it would be more user friendly to check if a process with
such name is running and at least print a warning, or even skip the
test.

I suppose that we can add a library function that would loop over
/proc/*/comm and return true if we find a match.

> + */
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <signal.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include "../include/mem.h"
> +#include "ksm_common.h"
> +
> +/* This test allocates one page, fills the page with a's, captures the
> + * full_scan and pages_skipped counters. Then it makes sure at least 3
> + * full scans have been performed and measures the above counters again.
> + * The expectation is that at least 50% of the pages are skipped.
> + *
> + * To wait for at least 3 scans it uses the wait_ksmd_full_scan() function. In
> + * reality, it will be a lot more scans as the wait_ksmd_full_scan() function
> + * sleeps for one second.
> + */
> +static void create_memory(void)
> +{
> +	int status;
> +	int full_scans_begin;
> +	int full_scans_end;
> +	int pages_skipped_begin;
> +	int pages_skipped_end;
> +	int diff_pages;
> +	int diff_scans;
> +	unsigned long page_size;
> +	char *memory;
> +
> +	/* Apply for the space for memory. */
> +	page_size = sysconf(_SC_PAGE_SIZE);
> +	memory = SAFE_MALLOC(page_size);
> +
> +	for (int i = 0; i < 1; i++) {
> +		memory = SAFE_MMAP(NULL, page_size, PROT_READ|PROT_WRITE,
> +			MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> +#ifdef HAVE_DECL_MADV_MERGEABLE
> +		if (madvise(memory, page_size, MADV_MERGEABLE) == -1)
> +			tst_brk(TBROK|TERRNO, "madvise");
> +#endif
> +	}
> +	memset(memory, 'a', page_size);
> +
> +	tst_res(TINFO, "KSM merging...");
> +	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
> +		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
> +	}
> +
> +	/* Set defalut ksm scan values. */
> +	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
> +	SAFE_FILE_PRINTF(PATH_KSM "pages_to_scan", "%ld", 100l);
> +	SAFE_FILE_PRINTF(PATH_KSM "sleep_millisecs", "0");
> +
> +	/* Measure pages skipped aka "smart scan". */
> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_begin);
> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
> +	wait_ksmd_full_scan();
> +
> +	tst_res(TINFO, "stop KSM.");
> +	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
> +
> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_end);
> +	diff_pages = pages_skipped_end - pages_skipped_begin;
> +	diff_scans = full_scans_end - full_scans_begin;
> +
> +	if (diff_pages < diff_scans * 50 / 100) {
> +		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
> +	} else {
> +		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
> +	}
> +
> +	while (waitpid(-1, &status, 0) > 0)
> +		if (WEXITSTATUS(status) != 0)
> +			tst_res(TFAIL, "child exit status is %d",
> +					WEXITSTATUS(status));

Does the test fork a child? I do not see any place in the code that
would do so, did I miss something?

> +}
> +
> +static void verify_ksm(void)
> +{
> +	create_memory();

This is useless indirection.

> +}
> +
> +static struct tst_test test = {
> +	.needs_root = 1,
> +	.forks_child = 1,
> +	.options = (struct tst_option[]) {
> +		{}
> +	},
> +	.save_restore = (const struct tst_path_val[]) {
> +		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
> +		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
> +		{"/sys/kernel/mm/ksm/smart_scan", "1",
> +			TST_SR_SKIP_MISSING | TST_SR_TCONF},
> +		{}
> +	},
> +	.needs_kconfigs = (const char *const[]){
> +		"CONFIG_KSM=y",
> +		NULL
> +	},
> +	.test_all = verify_ksm,
> +};
> -- 
> 2.39.3
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz

Re: [PATCH v3 1/2] mem: disable KSM smart scan for ksm tests

[Petr Vorel]

Hi Stefan,

> This disables the "smart scan" KSM feature to make sure that the volatile
> count remains at 0.

Merged this one, thank you!

Kind regards,
Petr

Re: [PATCH v3 2/2] add ksm test for smart-scan feature

[Petr Vorel]

Hi Stefan,

> This adds a new ksm (kernel samepage merging) test to evaluate the new
> smart scan feature. It allocates a page and fills it with 'a'
> characters. It captures the pages_skipped counter, waits for a few
> iterations and captures the pages_skipped counter again. The expectation
> is that over 50% of the page scans are skipped (There is only one page
> that has KSM enabled and it gets scanned during each iteration and it
> cannot be de-duplicated).

> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> ---
>  runtest/mm                       |   1 +
>  testcases/kernel/mem/.gitignore  |   1 +
>  testcases/kernel/mem/ksm/ksm07.c | 131 +++++++++++++++++++++++++++++++
>  3 files changed, 133 insertions(+)
>  create mode 100644 testcases/kernel/mem/ksm/ksm07.c

> diff --git a/runtest/mm b/runtest/mm
> index f288fed36..d859b331c 100644
> --- a/runtest/mm
> +++ b/runtest/mm
> @@ -70,6 +70,7 @@ ksm05 ksm05 -I 10
>  ksm06 ksm06
>  ksm06_1 ksm06 -n 10
>  ksm06_2 ksm06 -n 8000
> +ksm07 ksm07

>  cpuset01 cpuset01

> diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
> index 7258489ed..c96fe8bfc 100644
> --- a/testcases/kernel/mem/.gitignore
> +++ b/testcases/kernel/mem/.gitignore
> @@ -53,6 +53,7 @@
>  /ksm/ksm04
>  /ksm/ksm05
>  /ksm/ksm06
> +/ksm/ksm07
>  /mem/mem02
>  /mmapstress/mmap-corruption01
>  /mmapstress/mmapstress01
> diff --git a/testcases/kernel/mem/ksm/ksm07.c b/testcases/kernel/mem/ksm/ksm07.c
> new file mode 100644
> index 000000000..16153fdb2
> --- /dev/null
> +++ b/testcases/kernel/mem/ksm/ksm07.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2010-2017  Red Hat, Inc.
> + */
> +/*\
> + * [Description]
> + *
> + * Kernel Samepage Merging (KSM)
> + *
> + * This adds a new ksm (kernel samepage merging) test to evaluate the new
> + * smart scan feature. It allocates a page and fills it with 'a'
> + * characters. It captures the pages_skipped counter, waits for a few
> + * iterations and captures the pages_skipped counter again. The expectation
> + * is that over 50% of the page scans are skipped (There is only one page
> + * that has KSM enabled and it gets scanned during each iteration and it
> + * cannot be de-duplicated).
> + *
> + * Prerequisites:
> + *
> + * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
> + *    distrub the testing as they also change some ksm tunables depends
> + *    on current workloads.
> + */
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <signal.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include "../include/mem.h"
> +#include "ksm_common.h"
> +
> +/* This test allocates one page, fills the page with a's, captures the
> + * full_scan and pages_skipped counters. Then it makes sure at least 3
> + * full scans have been performed and measures the above counters again.
> + * The expectation is that at least 50% of the pages are skipped.
> + *
> + * To wait for at least 3 scans it uses the wait_ksmd_full_scan() function. In
> + * reality, it will be a lot more scans as the wait_ksmd_full_scan() function
> + * sleeps for one second.
> + */
> +static void create_memory(void)
> +{
> +	int status;
> +	int full_scans_begin;
> +	int full_scans_end;
> +	int pages_skipped_begin;
> +	int pages_skipped_end;
> +	int diff_pages;
> +	int diff_scans;
> +	unsigned long page_size;
> +	char *memory;
> +
> +	/* Apply for the space for memory. */
> +	page_size = sysconf(_SC_PAGE_SIZE);
> +	memory = SAFE_MALLOC(page_size);
> +
> +	for (int i = 0; i < 1; i++) {
> +		memory = SAFE_MMAP(NULL, page_size, PROT_READ|PROT_WRITE,
> +			MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> +#ifdef HAVE_DECL_MADV_MERGEABLE
> +		if (madvise(memory, page_size, MADV_MERGEABLE) == -1)
> +			tst_brk(TBROK|TERRNO, "madvise");
> +#endif
> +	}
> +	memset(memory, 'a', page_size);
> +
> +	tst_res(TINFO, "KSM merging...");
> +	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
> +		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
> +	}
> +
> +	/* Set defalut ksm scan values. */
> +	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
> +	SAFE_FILE_PRINTF(PATH_KSM "pages_to_scan", "%ld", 100l);
> +	SAFE_FILE_PRINTF(PATH_KSM "sleep_millisecs", "0");
> +
> +	/* Measure pages skipped aka "smart scan". */
> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_begin);
> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
Unfortunately SAFE_FILE_SCANF quits on missing file and
/sys/kernel/mm/ksm/pages_skipped is not on kernel < 6.7.

safe_file_vprintf() which SAFE_FILE_SCANF() internally uses does not support any
flag to quit with TCONF instead TBROK when /sys/kernel/mm/ksm/pages_skipped does
not exists.

We could use access() in setup function, but another line in .save_restore will
help:

{PATH_KSM "pages_skipped", NULL, TST_SR_TCONF}

> +	wait_ksmd_full_scan();
> +
> +	tst_res(TINFO, "stop KSM.");
> +	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
> +
> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_end);
> +	diff_pages = pages_skipped_end - pages_skipped_begin;
> +	diff_scans = full_scans_end - full_scans_begin;

I was going to merge this (with minor cleanup), but the only remaining issue is
that we allow to test run repeatedly via -iN:

# ./ksm07 -i2
tst_test.c:1574: TINFO: Timeout per run is 0h 00m 30s
ksm07.c:73: TINFO: KSM merging...
ksm_helper.c:36: TINFO: ksm daemon takes 1s to run two full scans
ksm07.c:88: TINFO: stop KSM.
ksm07.c:99: TPASS: smart_scan skipped more than 50% of the pages.
ksm07.c:73: TINFO: KSM merging...
ksm_helper.c:36: TINFO: ksm daemon takes 1s to run two full scans
ksm07.c:88: TINFO: stop KSM.
ksm07.c:97: TFAIL: not enough pages have been skipped by smart_scan.

I'm confused, how to reset KSM to be able to run the test more times?

> +
> +	if (diff_pages < diff_scans * 50 / 100) {
> +		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
> +	} else {
> +		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
> +	}
> +
> +	while (waitpid(-1, &status, 0) > 0)
> +		if (WEXITSTATUS(status) != 0)
> +			tst_res(TFAIL, "child exit status is %d",
> +					WEXITSTATUS(status));
> +}
This is not needed, done by check_child_status() in
lib/tst_test.c.

> +
> +static void verify_ksm(void)
> +{
> +	create_memory();
> +}
Why this wrapper? "verify_" as a pattern name is not a must.
> +
> +static struct tst_test test = {
> +	.needs_root = 1,
> +	.forks_child = 1,
> +	.options = (struct tst_option[]) {
> +		{}
> +	},
> +	.save_restore = (const struct tst_path_val[]) {
> +		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
> +		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
> +		{"/sys/kernel/mm/ksm/smart_scan", "1",
We have PATH_KSM definition, lets use it.

> +			TST_SR_SKIP_MISSING | TST_SR_TCONF},
> +		{}
> +	},
> +	.needs_kconfigs = (const char *const[]){
> +		"CONFIG_KSM=y",
> +		NULL
> +	},
> +	.test_all = verify_ksm,
> +};

I was going to merge your patch with following changes.
We just need solve -i2 issue.

Kind regards,
Petr

diff --git testcases/kernel/mem/ksm/ksm07.c testcases/kernel/mem/ksm/ksm07.c
index 16153fdb2..e5c31775b 100644
--- testcases/kernel/mem/ksm/ksm07.c
+++ testcases/kernel/mem/ksm/ksm07.c
@@ -5,35 +5,25 @@
 /*\
  * [Description]
  *
- * Kernel Samepage Merging (KSM)
+ * Kernel Samepage Merging (KSM) for smart scan feature
  *
- * This adds a new ksm (kernel samepage merging) test to evaluate the new
- * smart scan feature. It allocates a page and fills it with 'a'
- * characters. It captures the pages_skipped counter, waits for a few
- * iterations and captures the pages_skipped counter again. The expectation
- * is that over 50% of the page scans are skipped (There is only one page
- * that has KSM enabled and it gets scanned during each iteration and it
- * cannot be de-duplicated).
+ * Test allocates a page and fills it with 'a' characters. It captures the
+ * pages_skipped counter, waits for a few  iterations and captures the
+ * pages_skipped counter again. The expectation  is that over 50% of the page
+ * scans are skipped. (There is only one page that has KSM enabled and it gets
+ * scanned during each iteration and it cannot be de-duplicated.)
  *
- * Prerequisites:
+ * Smart scan feature was added in kernel v6.7.
  *
- * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
- *    distrub the testing as they also change some ksm tunables depends
- *    on current workloads.
+ * [Prerequisites]
+ *
+ * ksm and ksmtuned daemons need to be disabled. Otherwise, it could
+ * distrub the testing as they also change some ksm tunables depends
+ * on current workloads.
  */
-#include <sys/types.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
+
 #include <sys/wait.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include "../include/mem.h"
-#include "ksm_common.h"
+#include "mem.h"
 
 /* This test allocates one page, fills the page with a's, captures the
  * full_scan and pages_skipped counters. Then it makes sure at least 3
@@ -46,7 +36,6 @@
  */
 static void create_memory(void)
 {
-	int status;
 	int full_scans_begin;
 	int full_scans_end;
 	int pages_skipped_begin;
@@ -70,10 +59,10 @@ static void create_memory(void)
 	}
 	memset(memory, 'a', page_size);
 
-	tst_res(TINFO, "KSM merging...");
-	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
+	tst_res(TINFO, "KSM merging");
+
+	if (access(PATH_KSM "max_page_sharing", F_OK) == 0)
 		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
-	}
 
 	/* Set defalut ksm scan values. */
 	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
@@ -85,7 +74,7 @@ static void create_memory(void)
 	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
 	wait_ksmd_full_scan();
 
-	tst_res(TINFO, "stop KSM.");
+	tst_res(TINFO, "stop KSM");
 	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
 
 	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
@@ -93,21 +82,10 @@ static void create_memory(void)
 	diff_pages = pages_skipped_end - pages_skipped_begin;
 	diff_scans = full_scans_end - full_scans_begin;
 
-	if (diff_pages < diff_scans * 50 / 100) {
-		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
-	} else {
-		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
-	}
-
-	while (waitpid(-1, &status, 0) > 0)
-		if (WEXITSTATUS(status) != 0)
-			tst_res(TFAIL, "child exit status is %d",
-					WEXITSTATUS(status));
-}
-
-static void verify_ksm(void)
-{
-	create_memory();
+	if (diff_pages < diff_scans * 50 / 100)
+		tst_res(TFAIL, "not enough pages have been skipped by smart_scan");
+	else
+		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages");
 }
 
 static struct tst_test test = {
@@ -117,9 +95,10 @@ static struct tst_test test = {
 		{}
 	},
 	.save_restore = (const struct tst_path_val[]) {
-		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
-		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
-		{"/sys/kernel/mm/ksm/smart_scan", "1",
+		{PATH_KSM "pages_skipped", NULL, TST_SR_TCONF},
+		{PATH_KSM "run", NULL, TST_SR_TCONF},
+		{PATH_KSM "sleep_millisecs", NULL, TST_SR_TCONF},
+		{PATH_KSM "smart_scan", "1",
 			TST_SR_SKIP_MISSING | TST_SR_TCONF},
 		{}
 	},
@@ -127,5 +106,5 @@ static struct tst_test test = {
 		"CONFIG_KSM=y",
 		NULL
 	},
-	.test_all = verify_ksm,
+	.test_all = create_memory,
 };

Re: [LTP] [PATCH v3 2/2] add ksm test for smart-scan feature

[Petr Vorel]

Hi all,

...
> > +
> > +	while (waitpid(-1, &status, 0) > 0)
> > +		if (WEXITSTATUS(status) != 0)
> > +			tst_res(TFAIL, "child exit status is %d",
> > +					WEXITSTATUS(status));

> Does the test fork a child? I do not see any place in the code that
> would do so, did I miss something?

Ah, I also pointed out this is useless, but forget to point out that
.forks_child = 1 should be also removed.

Kind regards,
Petr

Re: [PATCH v3 2/2] add ksm test for smart-scan feature

[Stefan Roesch]

On Tue, Dec 5, 2023, at 5:16 AM, Petr Vorel wrote:
> Hi Stefan,
>
>> This adds a new ksm (kernel samepage merging) test to evaluate the new
>> smart scan feature. It allocates a page and fills it with 'a'
>> characters. It captures the pages_skipped counter, waits for a few
>> iterations and captures the pages_skipped counter again. The expectation
>> is that over 50% of the page scans are skipped (There is only one page
>> that has KSM enabled and it gets scanned during each iteration and it
>> cannot be de-duplicated).
>
>> Signed-off-by: Stefan Roesch <shr@devkernel.io>
>> ---
>>  runtest/mm                       |   1 +
>>  testcases/kernel/mem/.gitignore  |   1 +
>>  testcases/kernel/mem/ksm/ksm07.c | 131 +++++++++++++++++++++++++++++++
>>  3 files changed, 133 insertions(+)
>>  create mode 100644 testcases/kernel/mem/ksm/ksm07.c
>
>> diff --git a/runtest/mm b/runtest/mm
>> index f288fed36..d859b331c 100644
>> --- a/runtest/mm
>> +++ b/runtest/mm
>> @@ -70,6 +70,7 @@ ksm05 ksm05 -I 10
>>  ksm06 ksm06
>>  ksm06_1 ksm06 -n 10
>>  ksm06_2 ksm06 -n 8000
>> +ksm07 ksm07
>
>>  cpuset01 cpuset01
>
>> diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
>> index 7258489ed..c96fe8bfc 100644
>> --- a/testcases/kernel/mem/.gitignore
>> +++ b/testcases/kernel/mem/.gitignore
>> @@ -53,6 +53,7 @@
>>  /ksm/ksm04
>>  /ksm/ksm05
>>  /ksm/ksm06
>> +/ksm/ksm07
>>  /mem/mem02
>>  /mmapstress/mmap-corruption01
>>  /mmapstress/mmapstress01
>> diff --git a/testcases/kernel/mem/ksm/ksm07.c b/testcases/kernel/mem/ksm/ksm07.c
>> new file mode 100644
>> index 000000000..16153fdb2
>> --- /dev/null
>> +++ b/testcases/kernel/mem/ksm/ksm07.c
>> @@ -0,0 +1,131 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * Copyright (C) 2010-2017  Red Hat, Inc.
>> + */
>> +/*\
>> + * [Description]
>> + *
>> + * Kernel Samepage Merging (KSM)
>> + *
>> + * This adds a new ksm (kernel samepage merging) test to evaluate the new
>> + * smart scan feature. It allocates a page and fills it with 'a'
>> + * characters. It captures the pages_skipped counter, waits for a few
>> + * iterations and captures the pages_skipped counter again. The expectation
>> + * is that over 50% of the page scans are skipped (There is only one page
>> + * that has KSM enabled and it gets scanned during each iteration and it
>> + * cannot be de-duplicated).
>> + *
>> + * Prerequisites:
>> + *
>> + * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
>> + *    distrub the testing as they also change some ksm tunables depends
>> + *    on current workloads.
>> + */
>> +#include <sys/types.h>
>> +#include <sys/mman.h>
>> +#include <sys/stat.h>
>> +#include <sys/wait.h>
>> +#include <errno.h>
>> +#include <fcntl.h>
>> +#include <signal.h>
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +#include "../include/mem.h"
>> +#include "ksm_common.h"
>> +
>> +/* This test allocates one page, fills the page with a's, captures the
>> + * full_scan and pages_skipped counters. Then it makes sure at least 3
>> + * full scans have been performed and measures the above counters again.
>> + * The expectation is that at least 50% of the pages are skipped.
>> + *
>> + * To wait for at least 3 scans it uses the wait_ksmd_full_scan() function. In
>> + * reality, it will be a lot more scans as the wait_ksmd_full_scan() function
>> + * sleeps for one second.
>> + */
>> +static void create_memory(void)
>> +{
>> +	int status;
>> +	int full_scans_begin;
>> +	int full_scans_end;
>> +	int pages_skipped_begin;
>> +	int pages_skipped_end;
>> +	int diff_pages;
>> +	int diff_scans;
>> +	unsigned long page_size;
>> +	char *memory;
>> +
>> +	/* Apply for the space for memory. */
>> +	page_size = sysconf(_SC_PAGE_SIZE);
>> +	memory = SAFE_MALLOC(page_size);
>> +
>> +	for (int i = 0; i < 1; i++) {
>> +		memory = SAFE_MMAP(NULL, page_size, PROT_READ|PROT_WRITE,
>> +			MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
>> +#ifdef HAVE_DECL_MADV_MERGEABLE
>> +		if (madvise(memory, page_size, MADV_MERGEABLE) == -1)
>> +			tst_brk(TBROK|TERRNO, "madvise");
>> +#endif
>> +	}
>> +	memset(memory, 'a', page_size);
>> +
>> +	tst_res(TINFO, "KSM merging...");
>> +	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
>> +		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
>> +	}
>> +
>> +	/* Set defalut ksm scan values. */
>> +	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
>> +	SAFE_FILE_PRINTF(PATH_KSM "pages_to_scan", "%ld", 100l);
>> +	SAFE_FILE_PRINTF(PATH_KSM "sleep_millisecs", "0");
>> +
>> +	/* Measure pages skipped aka "smart scan". */
>> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_begin);
>> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
> Unfortunately SAFE_FILE_SCANF quits on missing file and
> /sys/kernel/mm/ksm/pages_skipped is not on kernel < 6.7.
>
> safe_file_vprintf() which SAFE_FILE_SCANF() internally uses does not support any
> flag to quit with TCONF instead TBROK when /sys/kernel/mm/ksm/pages_skipped does
> not exists.
>
> We could use access() in setup function, but another line in .save_restore will
> help:
>
> {PATH_KSM "pages_skipped", NULL, TST_SR_TCONF}
>

I don't think this works correctly. I see a warning:

tst_sys_conf.c:144: TINFO: Failed to open FILE '/sys/kernel/mm/ksm/pages_skipped'

The difference to the other ksm files is, that this is not writeable.

>> +	wait_ksmd_full_scan();
>> +
>> +	tst_res(TINFO, "stop KSM.");
>> +	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
>> +
>> +	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
>> +	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_end);
>> +	diff_pages = pages_skipped_end - pages_skipped_begin;
>> +	diff_scans = full_scans_end - full_scans_begin;
>
> I was going to merge this (with minor cleanup), but the only remaining issue is
> that we allow to test run repeatedly via -iN:
>
> # ./ksm07 -i2
> tst_test.c:1574: TINFO: Timeout per run is 0h 00m 30s
> ksm07.c:73: TINFO: KSM merging...
> ksm_helper.c:36: TINFO: ksm daemon takes 1s to run two full scans
> ksm07.c:88: TINFO: stop KSM.
> ksm07.c:99: TPASS: smart_scan skipped more than 50% of the pages.
> ksm07.c:73: TINFO: KSM merging...
> ksm_helper.c:36: TINFO: ksm daemon takes 1s to run two full scans
> ksm07.c:88: TINFO: stop KSM.
> ksm07.c:97: TFAIL: not enough pages have been skipped by smart_scan.
>
> I'm confused, how to reset KSM to be able to run the test more times?
>
>> +
>> +	if (diff_pages < diff_scans * 50 / 100) {
>> +		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
>> +	} else {
>> +		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
>> +	}
>> +
>> +	while (waitpid(-1, &status, 0) > 0)
>> +		if (WEXITSTATUS(status) != 0)
>> +			tst_res(TFAIL, "child exit status is %d",
>> +					WEXITSTATUS(status));
>> +}
> This is not needed, done by check_child_status() in
> lib/tst_test.c.
>
>> +
>> +static void verify_ksm(void)
>> +{
>> +	create_memory();
>> +}
> Why this wrapper? "verify_" as a pattern name is not a must.
>> +
>> +static struct tst_test test = {
>> +	.needs_root = 1,
>> +	.forks_child = 1,
>> +	.options = (struct tst_option[]) {
>> +		{}
>> +	},
>> +	.save_restore = (const struct tst_path_val[]) {
>> +		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
>> +		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
>> +		{"/sys/kernel/mm/ksm/smart_scan", "1",
> We have PATH_KSM definition, lets use it.
>
>> +			TST_SR_SKIP_MISSING | TST_SR_TCONF},
>> +		{}
>> +	},
>> +	.needs_kconfigs = (const char *const[]){
>> +		"CONFIG_KSM=y",
>> +		NULL
>> +	},
>> +	.test_all = verify_ksm,
>> +};
>
> I was going to merge your patch with following changes.
> We just need solve -i2 issue.
>

I have a solution for this: we need another madvise call at the end. I'll send
it with the next version.

> Kind regards,
> Petr
>
> diff --git testcases/kernel/mem/ksm/ksm07.c testcases/kernel/mem/ksm/ksm07.c
> index 16153fdb2..e5c31775b 100644
> --- testcases/kernel/mem/ksm/ksm07.c
> +++ testcases/kernel/mem/ksm/ksm07.c
> @@ -5,35 +5,25 @@
>  /*\
>   * [Description]
>   *
> - * Kernel Samepage Merging (KSM)
> + * Kernel Samepage Merging (KSM) for smart scan feature
>   *
> - * This adds a new ksm (kernel samepage merging) test to evaluate the new
> - * smart scan feature. It allocates a page and fills it with 'a'
> - * characters. It captures the pages_skipped counter, waits for a few
> - * iterations and captures the pages_skipped counter again. The expectation
> - * is that over 50% of the page scans are skipped (There is only one page
> - * that has KSM enabled and it gets scanned during each iteration and it
> - * cannot be de-duplicated).
> + * Test allocates a page and fills it with 'a' characters. It captures the
> + * pages_skipped counter, waits for a few  iterations and captures the
> + * pages_skipped counter again. The expectation  is that over 50% of the page
> + * scans are skipped. (There is only one page that has KSM enabled and it gets
> + * scanned during each iteration and it cannot be de-duplicated.)
>   *
> - * Prerequisites:
> + * Smart scan feature was added in kernel v6.7.
>   *
> - * 1) ksm and ksmtuned daemons need to be disabled. Otherwise, it could
> - *    distrub the testing as they also change some ksm tunables depends
> - *    on current workloads.
> + * [Prerequisites]
> + *
> + * ksm and ksmtuned daemons need to be disabled. Otherwise, it could
> + * distrub the testing as they also change some ksm tunables depends
> + * on current workloads.
>   */
> -#include <sys/types.h>
> -#include <sys/mman.h>
> -#include <sys/stat.h>
> +
>  #include <sys/wait.h>
> -#include <errno.h>
> -#include <fcntl.h>
> -#include <signal.h>
> -#include <stdio.h>
> -#include <stdlib.h>
> -#include <string.h>
> -#include <unistd.h>
> -#include "../include/mem.h"
> -#include "ksm_common.h"
> +#include "mem.h"
> 
>  /* This test allocates one page, fills the page with a's, captures the
>   * full_scan and pages_skipped counters. Then it makes sure at least 3
> @@ -46,7 +36,6 @@
>   */
>  static void create_memory(void)
>  {
> -	int status;
>  	int full_scans_begin;
>  	int full_scans_end;
>  	int pages_skipped_begin;
> @@ -70,10 +59,10 @@ static void create_memory(void)
>  	}
>  	memset(memory, 'a', page_size);
> 
> -	tst_res(TINFO, "KSM merging...");
> -	if (access(PATH_KSM "max_page_sharing", F_OK) == 0) {
> +	tst_res(TINFO, "KSM merging");
> +
> +	if (access(PATH_KSM "max_page_sharing", F_OK) == 0)
>  		SAFE_FILE_PRINTF(PATH_KSM "run", "2");
> -	}
> 
>  	/* Set defalut ksm scan values. */
>  	SAFE_FILE_PRINTF(PATH_KSM "run", "1");
> @@ -85,7 +74,7 @@ static void create_memory(void)
>  	SAFE_FILE_SCANF(PATH_KSM "pages_skipped", "%d", &pages_skipped_begin);
>  	wait_ksmd_full_scan();
> 
> -	tst_res(TINFO, "stop KSM.");
> +	tst_res(TINFO, "stop KSM");
>  	SAFE_FILE_PRINTF(PATH_KSM "run", "0");
> 
>  	SAFE_FILE_SCANF(PATH_KSM "full_scans", "%d", &full_scans_end);
> @@ -93,21 +82,10 @@ static void create_memory(void)
>  	diff_pages = pages_skipped_end - pages_skipped_begin;
>  	diff_scans = full_scans_end - full_scans_begin;
> 
> -	if (diff_pages < diff_scans * 50 / 100) {
> -		tst_res(TFAIL, "not enough pages have been skipped by smart_scan.");
> -	} else {
> -		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages.");
> -	}
> -
> -	while (waitpid(-1, &status, 0) > 0)
> -		if (WEXITSTATUS(status) != 0)
> -			tst_res(TFAIL, "child exit status is %d",
> -					WEXITSTATUS(status));
> -}
> -
> -static void verify_ksm(void)
> -{
> -	create_memory();
> +	if (diff_pages < diff_scans * 50 / 100)
> +		tst_res(TFAIL, "not enough pages have been skipped by smart_scan");
> +	else
> +		tst_res(TPASS, "smart_scan skipped more than 50%% of the pages");
>  }
> 
>  static struct tst_test test = {
> @@ -117,9 +95,10 @@ static struct tst_test test = {
>  		{}
>  	},
>  	.save_restore = (const struct tst_path_val[]) {
> -		{"/sys/kernel/mm/ksm/run", NULL, TST_SR_TCONF},
> -		{"/sys/kernel/mm/ksm/sleep_millisecs", NULL, TST_SR_TCONF},
> -		{"/sys/kernel/mm/ksm/smart_scan", "1",
> +		{PATH_KSM "pages_skipped", NULL, TST_SR_TCONF},
> +		{PATH_KSM "run", NULL, TST_SR_TCONF},
> +		{PATH_KSM "sleep_millisecs", NULL, TST_SR_TCONF},
> +		{PATH_KSM "smart_scan", "1",
>  			TST_SR_SKIP_MISSING | TST_SR_TCONF},
>  		{}
>  	},
> @@ -127,5 +106,5 @@ static struct tst_test test = {
>  		"CONFIG_KSM=y",
>  		NULL
>  	},
> -	.test_all = verify_ksm,
> +	.test_all = create_memory,
>  };