[LTP] [PATCH v3 2/2] add ksm test for smart-scan feature
Petr Vorel
pvorel@suse.cz
Tue Dec 5 14:16:08 CET 2023
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,
};
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