diff mbox series

[v3,3/3] selftests: add zswapin and no zswap tests

Message ID 20240205225608.3083251-4-nphamcs@gmail.com
State New
Headers
Series [v3,1/3] selftests: zswap: add zswap selftest file to zswap maintainer entry |

Commit Message

Nhat Pham Feb. 5, 2024, 10:56 p.m. UTC 
  Add a selftest to cover the zswapin code path, allocating more memory
than the cgroup limit to trigger swapout/zswapout, then reading the
pages back in memory several times. This is inspired by a recently
encountered kernel crash on the zswapin path in our internal kernel,
which went undetected because of a lack of test coverage for this path.

Add a selftest to verify that when memory.zswap.max = 0, no pages can go
to the zswap pool for the cgroup.

Suggested-by: Rik van Riel <riel@surriel.com>
Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)

Comments

Yosry Ahmed Feb. 5, 2024, 11:05 p.m. UTC | #1 
On Mon, Feb 05, 2024 at 02:56:08PM -0800, Nhat Pham wrote:
> Add a selftest to cover the zswapin code path, allocating more memory
> than the cgroup limit to trigger swapout/zswapout, then reading the
> pages back in memory several times. This is inspired by a recently
> encountered kernel crash on the zswapin path in our internal kernel,
> which went undetected because of a lack of test coverage for this path.
> 
> Add a selftest to verify that when memory.zswap.max = 0, no pages can go
> to the zswap pool for the cgroup.
> 
> Suggested-by: Rik van Riel <riel@surriel.com>
> Suggested-by: Yosry Ahmed <yosryahmed@google.com>
> Signed-off-by: Nhat Pham <nphamcs@gmail.com>

LGTM with a few nits below:
Acked-by: Yosry Ahmed <yosryahmed@google.com>

Thanks!

> ---
>  tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++-
>  1 file changed, 119 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
> index 32ce975b21d1..c263610a4a60 100644
> --- a/tools/testing/selftests/cgroup/test_zswap.c
> +++ b/tools/testing/selftests/cgroup/test_zswap.c
> @@ -60,6 +60,27 @@ static long get_zswpout(const char *cgroup)
>  	return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
>  }
>  
> +static int allocate_and_read_bytes(const char *cgroup, void *arg)
> +{
> +	size_t size = (size_t)arg;
> +	char *mem = (char *)malloc(size);
> +	int ret = 0;
> +
> +	if (!mem)
> +		return -1;
> +	for (int i = 0; i < size; i += 4095)
> +		mem[i] = 'a';
> +
> +	/* go through the allocated memory to (z)swap in and out pages */

nit: s/go/Go

> +	for (int i = 0; i < size; i += 4095) {
> +		if (mem[i] != 'a')
> +			ret = -1;
> +	}
> +
> +	free(mem);
> +	return ret;
> +}
> +
>  static int allocate_bytes(const char *cgroup, void *arg)
>  {
>  	size_t size = (size_t)arg;
> @@ -100,7 +121,6 @@ static int test_zswap_usage(const char *root)
>  	int ret = KSFT_FAIL;
>  	char *test_group;
>  
> -	/* Set up */

We removed this comment here.

>  	test_group = cg_name(root, "no_shrink_test");
>  	if (!test_group)
>  		goto out;
> @@ -133,6 +153,102 @@ static int test_zswap_usage(const char *root)
>  	return ret;
>  }
>  
> +/*
> + * Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
> + * the cgroup.
> + */
> +static int test_swapin_nozswap(const char *root)
> +{
> +	int ret = KSFT_FAIL;
> +	char *test_group;
> +	long swap_peak, zswpout;
> +
> +	test_group = cg_name(root, "no_zswap_test");
> +	if (!test_group)
> +		goto out;
> +	if (cg_create(test_group))
> +		goto out;
> +	if (cg_write(test_group, "memory.max", "8M"))
> +		goto out;
> +	if (cg_write(test_group, "memory.zswap.max", "0"))
> +		goto out;
> +
> +	/* Allocate and read more than memory.max to trigger swapin */
> +	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
> +		goto out;
> +
> +	/* Verify that pages are swapped out, but no zswap happened */
> +	swap_peak = cg_read_long(test_group, "memory.swap.peak");
> +	if (swap_peak < 0) {
> +		ksft_print_msg("failed to get cgroup's swap_peak\n");
> +		goto out;
> +	}
> +
> +	if (swap_peak == 0) {
> +		ksft_print_msg("pages should be swapped out\n");
> +		goto out;
> +	}

We can actually check that this number is >= 24M instead. Not a big
deal, but might as well.

> +
> +	zswpout = get_zswpout(test_group);
> +	if (zswpout < 0) {
> +		ksft_print_msg("failed to get zswpout\n");
> +		goto out;
> +	}
> +
> +	if (zswpout > 0) {
> +		ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
> +		goto out;
> +	}
> +
> +	ret = KSFT_PASS;
> +
> +out:
> +	cg_destroy(test_group);
> +	free(test_group);
> +	return ret;
> +}
> +
> +/* Simple test to verify the (z)swapin code paths */
> +static int test_zswapin(const char *root)
> +{
> +	int ret = KSFT_FAIL;
> +	char *test_group;
> +	long zswpin;
> +
> +	/* Set up */

Yet we added a similar one here :)

> +	test_group = cg_name(root, "zswapin_test");
> +	if (!test_group)
> +		goto out;
> +	if (cg_create(test_group))
> +		goto out;
> +	if (cg_write(test_group, "memory.max", "8M"))
> +		goto out;
> +	if (cg_write(test_group, "memory.zswap.max", "max"))
> +		goto out;
> +
> +	/* Allocate and read more than memory.max to trigger (z)swap in */
> +	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
> +		goto out;
> +
> +	zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
> +	if (zswpin < 0) {
> +		ksft_print_msg("failed to get zswpin\n");
> +		goto out;
> +	}
> +
> +	if (zswpin == 0) {
> +		ksft_print_msg("zswpin should not be 0\n");
> +		goto out;
> +	}

Same here, we can check that zswpin is at least 24M worth of events.
Again, not a big deal, but might as well.
Nhat Pham Feb. 5, 2024, 11:25 p.m. UTC | #2 
On Mon, Feb 5, 2024 at 3:05 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Mon, Feb 05, 2024 at 02:56:08PM -0800, Nhat Pham wrote:
> > Add a selftest to cover the zswapin code path, allocating more memory
> > than the cgroup limit to trigger swapout/zswapout, then reading the
> > pages back in memory several times. This is inspired by a recently
> > encountered kernel crash on the zswapin path in our internal kernel,
> > which went undetected because of a lack of test coverage for this path.
> >
> > Add a selftest to verify that when memory.zswap.max = 0, no pages can go
> > to the zswap pool for the cgroup.
> >
> > Suggested-by: Rik van Riel <riel@surriel.com>
> > Suggested-by: Yosry Ahmed <yosryahmed@google.com>
> > Signed-off-by: Nhat Pham <nphamcs@gmail.com>
>
> LGTM with a few nits below:
> Acked-by: Yosry Ahmed <yosryahmed@google.com>
>
> Thanks!
>
> > ---
> >  tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++-
> >  1 file changed, 119 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
> > index 32ce975b21d1..c263610a4a60 100644
> > --- a/tools/testing/selftests/cgroup/test_zswap.c
> > +++ b/tools/testing/selftests/cgroup/test_zswap.c
> > @@ -60,6 +60,27 @@ static long get_zswpout(const char *cgroup)
> >       return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
> >  }
> >
> > +static int allocate_and_read_bytes(const char *cgroup, void *arg)
> > +{
> > +     size_t size = (size_t)arg;
> > +     char *mem = (char *)malloc(size);
> > +     int ret = 0;
> > +
> > +     if (!mem)
> > +             return -1;
> > +     for (int i = 0; i < size; i += 4095)
> > +             mem[i] = 'a';
> > +
> > +     /* go through the allocated memory to (z)swap in and out pages */
>
> nit: s/go/Go
>
> > +     for (int i = 0; i < size; i += 4095) {
> > +             if (mem[i] != 'a')
> > +                     ret = -1;
> > +     }
> > +
> > +     free(mem);
> > +     return ret;
> > +}
> > +
> >  static int allocate_bytes(const char *cgroup, void *arg)
> >  {
> >       size_t size = (size_t)arg;
> > @@ -100,7 +121,6 @@ static int test_zswap_usage(const char *root)
> >       int ret = KSFT_FAIL;
> >       char *test_group;
> >
> > -     /* Set up */
>
> We removed this comment here.
>
> >       test_group = cg_name(root, "no_shrink_test");
> >       if (!test_group)
> >               goto out;
> > @@ -133,6 +153,102 @@ static int test_zswap_usage(const char *root)
> >       return ret;
> >  }
> >
> > +/*
> > + * Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
> > + * the cgroup.
> > + */
> > +static int test_swapin_nozswap(const char *root)
> > +{
> > +     int ret = KSFT_FAIL;
> > +     char *test_group;
> > +     long swap_peak, zswpout;
> > +
> > +     test_group = cg_name(root, "no_zswap_test");
> > +     if (!test_group)
> > +             goto out;
> > +     if (cg_create(test_group))
> > +             goto out;
> > +     if (cg_write(test_group, "memory.max", "8M"))
> > +             goto out;
> > +     if (cg_write(test_group, "memory.zswap.max", "0"))
> > +             goto out;
> > +
> > +     /* Allocate and read more than memory.max to trigger swapin */
> > +     if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
> > +             goto out;
> > +
> > +     /* Verify that pages are swapped out, but no zswap happened */
> > +     swap_peak = cg_read_long(test_group, "memory.swap.peak");
> > +     if (swap_peak < 0) {
> > +             ksft_print_msg("failed to get cgroup's swap_peak\n");
> > +             goto out;
> > +     }
> > +
> > +     if (swap_peak == 0) {
> > +             ksft_print_msg("pages should be swapped out\n");
> > +             goto out;
> > +     }
>
> We can actually check that this number is >= 24M instead. Not a big
> deal, but might as well.
>
> > +
> > +     zswpout = get_zswpout(test_group);
> > +     if (zswpout < 0) {
> > +             ksft_print_msg("failed to get zswpout\n");
> > +             goto out;
> > +     }
> > +
> > +     if (zswpout > 0) {
> > +             ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
> > +             goto out;
> > +     }
> > +
> > +     ret = KSFT_PASS;
> > +
> > +out:
> > +     cg_destroy(test_group);
> > +     free(test_group);
> > +     return ret;
> > +}
> > +
> > +/* Simple test to verify the (z)swapin code paths */
> > +static int test_zswapin(const char *root)
> > +{
> > +     int ret = KSFT_FAIL;
> > +     char *test_group;
> > +     long zswpin;
> > +
> > +     /* Set up */
>
> Yet we added a similar one here :)

Urgh I am stupid :) I meant to remove this, but accidentally removed
it from the old test instead :)


>
> > +     test_group = cg_name(root, "zswapin_test");
> > +     if (!test_group)
> > +             goto out;
> > +     if (cg_create(test_group))
> > +             goto out;
> > +     if (cg_write(test_group, "memory.max", "8M"))
> > +             goto out;
> > +     if (cg_write(test_group, "memory.zswap.max", "max"))
> > +             goto out;
> > +
> > +     /* Allocate and read more than memory.max to trigger (z)swap in */
> > +     if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
> > +             goto out;
> > +
> > +     zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
> > +     if (zswpin < 0) {
> > +             ksft_print_msg("failed to get zswpin\n");
> > +             goto out;
> > +     }
> > +
> > +     if (zswpin == 0) {
> > +             ksft_print_msg("zswpin should not be 0\n");
> > +             goto out;
> > +     }
>
> Same here, we can check that zswpin is at least 24M worth of events.
> Again, not a big deal, but might as well.
diff mbox series

Patch

diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
index 32ce975b21d1..c263610a4a60 100644
--- a/tools/testing/selftests/cgroup/test_zswap.c
+++ b/tools/testing/selftests/cgroup/test_zswap.c
@@ -60,6 +60,27 @@  static long get_zswpout(const char *cgroup)
 	return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
 }
 
+static int allocate_and_read_bytes(const char *cgroup, void *arg)
+{
+	size_t size = (size_t)arg;
+	char *mem = (char *)malloc(size);
+	int ret = 0;
+
+	if (!mem)
+		return -1;
+	for (int i = 0; i < size; i += 4095)
+		mem[i] = 'a';
+
+	/* go through the allocated memory to (z)swap in and out pages */
+	for (int i = 0; i < size; i += 4095) {
+		if (mem[i] != 'a')
+			ret = -1;
+	}
+
+	free(mem);
+	return ret;
+}
+
 static int allocate_bytes(const char *cgroup, void *arg)
 {
 	size_t size = (size_t)arg;
@@ -100,7 +121,6 @@  static int test_zswap_usage(const char *root)
 	int ret = KSFT_FAIL;
 	char *test_group;
 
-	/* Set up */
 	test_group = cg_name(root, "no_shrink_test");
 	if (!test_group)
 		goto out;
@@ -133,6 +153,102 @@  static int test_zswap_usage(const char *root)
 	return ret;
 }
 
+/*
+ * Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
+ * the cgroup.
+ */
+static int test_swapin_nozswap(const char *root)
+{
+	int ret = KSFT_FAIL;
+	char *test_group;
+	long swap_peak, zswpout;
+
+	test_group = cg_name(root, "no_zswap_test");
+	if (!test_group)
+		goto out;
+	if (cg_create(test_group))
+		goto out;
+	if (cg_write(test_group, "memory.max", "8M"))
+		goto out;
+	if (cg_write(test_group, "memory.zswap.max", "0"))
+		goto out;
+
+	/* Allocate and read more than memory.max to trigger swapin */
+	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
+		goto out;
+
+	/* Verify that pages are swapped out, but no zswap happened */
+	swap_peak = cg_read_long(test_group, "memory.swap.peak");
+	if (swap_peak < 0) {
+		ksft_print_msg("failed to get cgroup's swap_peak\n");
+		goto out;
+	}
+
+	if (swap_peak == 0) {
+		ksft_print_msg("pages should be swapped out\n");
+		goto out;
+	}
+
+	zswpout = get_zswpout(test_group);
+	if (zswpout < 0) {
+		ksft_print_msg("failed to get zswpout\n");
+		goto out;
+	}
+
+	if (zswpout > 0) {
+		ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
+		goto out;
+	}
+
+	ret = KSFT_PASS;
+
+out:
+	cg_destroy(test_group);
+	free(test_group);
+	return ret;
+}
+
+/* Simple test to verify the (z)swapin code paths */
+static int test_zswapin(const char *root)
+{
+	int ret = KSFT_FAIL;
+	char *test_group;
+	long zswpin;
+
+	/* Set up */
+	test_group = cg_name(root, "zswapin_test");
+	if (!test_group)
+		goto out;
+	if (cg_create(test_group))
+		goto out;
+	if (cg_write(test_group, "memory.max", "8M"))
+		goto out;
+	if (cg_write(test_group, "memory.zswap.max", "max"))
+		goto out;
+
+	/* Allocate and read more than memory.max to trigger (z)swap in */
+	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
+		goto out;
+
+	zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
+	if (zswpin < 0) {
+		ksft_print_msg("failed to get zswpin\n");
+		goto out;
+	}
+
+	if (zswpin == 0) {
+		ksft_print_msg("zswpin should not be 0\n");
+		goto out;
+	}
+
+	ret = KSFT_PASS;
+
+out:
+	cg_destroy(test_group);
+	free(test_group);
+	return ret;
+}
+
 /*
  * When trying to store a memcg page in zswap, if the memcg hits its memory
  * limit in zswap, writeback should affect only the zswapped pages of that
@@ -309,6 +425,8 @@  struct zswap_test {
 	const char *name;
 } tests[] = {
 	T(test_zswap_usage),
+	T(test_swapin_nozswap),
+	T(test_zswapin),
 	T(test_no_kmem_bypass),
 	T(test_no_invasive_cgroup_shrink),
 };