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 <[email protected]>
Suggested-by: Yosry Ahmed <[email protected]>
Signed-off-by: Nhat Pham <[email protected]>
---
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 */
+ 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),
};
--
2.39.3
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 <[email protected]>
> Suggested-by: Yosry Ahmed <[email protected]>
> Signed-off-by: Nhat Pham <[email protected]>
LGTM with a few nits below:
Acked-by: Yosry Ahmed <[email protected]>
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.
On Mon, Feb 5, 2024 at 3:05 PM Yosry Ahmed <[email protected]> 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 <[email protected]>
> > Suggested-by: Yosry Ahmed <[email protected]>
> > Signed-off-by: Nhat Pham <[email protected]>
>
> LGTM with a few nits below:
> Acked-by: Yosry Ahmed <[email protected]>
>
> 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.
Remove redundant "set up" comment and add check to ensure enough data is
swapped out (in swapin test) and zswapped-in.
Suggested-by: Yosry Ahmed <[email protected]>
Signed-off-by: Nhat Pham <[email protected]>
---
tools/testing/selftests/cgroup/test_zswap.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
index c263610a4a60..f0e488ed90d8 100644
--- a/tools/testing/selftests/cgroup/test_zswap.c
+++ b/tools/testing/selftests/cgroup/test_zswap.c
@@ -71,7 +71,7 @@ static int allocate_and_read_bytes(const char *cgroup, void *arg)
for (int i = 0; i < size; i += 4095)
mem[i] = 'a';
- /* go through the allocated memory to (z)swap in and out pages */
+ /* 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;
@@ -184,8 +184,8 @@ static int test_swapin_nozswap(const char *root)
goto out;
}
- if (swap_peak == 0) {
- ksft_print_msg("pages should be swapped out\n");
+ if (swap_peak < MB(24)) {
+ ksft_print_msg("at least 24MB of memory should be swapped out\n");
goto out;
}
@@ -215,7 +215,6 @@ static int test_zswapin(const char *root)
char *test_group;
long zswpin;
- /* Set up */
test_group = cg_name(root, "zswapin_test");
if (!test_group)
goto out;
@@ -236,8 +235,8 @@ static int test_zswapin(const char *root)
goto out;
}
- if (zswpin == 0) {
- ksft_print_msg("zswpin should not be 0\n");
+ if (zswpin < MB(24) / PAGE_SIZE) {
+ ksft_print_msg("at least 24MB should be brought back from zswap\n");
goto out;
}
@@ -260,7 +259,6 @@ static int test_no_invasive_cgroup_shrink(const char *root)
size_t control_allocation_size = MB(10);
char *control_allocation, *wb_group = NULL, *control_group = NULL;
- /* Set up */
wb_group = setup_test_group_1M(root, "per_memcg_wb_test1");
if (!wb_group)
return KSFT_FAIL;
base-commit: 9d193b36872d153e02e80c26203de4ee15127b58
--
2.40.1