[PATCH v3 0/5] memcontrol selftests fixups

[PATCH v3 0/5] memcontrol selftests fixups

[Michal Koutný]

Hello.

I'm just flushing the patches to make memcontrol selftests check the
events behavior we had consensus about (test_memcg_low fails).

(test_memcg_reclaim, test_memcg_swap_max fail for me now but it's present
even before the refactoring.)

The two bigger changes are:
- adjustment of the protected values to make tests succeed with the given
  tolerance,
- both test_memcg_low and test_memcg_min check protection of memory in
  populated cgroups (actually as per Documentation/admin-guide/cgroup-v2.rst
  memory.min should not apply to empty cgroups, which is not the case
  currently. Therefore I unified tests with the populated case in order to to
  bring more broken tests).

Thanks,
Michal

Changes from v2 (https://lore.kernel.org/r/20220518161859.21565-2-mkoutny@suse.com/)
- rebased on mm-stable 02e34fff195d3a5f67cbb553795dc109a37d1dcf
- collected acked-bys
- proper Fixes: tag

Changes from v1 (https://lore.kernel.org/r/20220513171811.730-1-mkoutny@suse.com/)
- fixed mis-rebase in compilation fix patch,
- added review, ack tags from v1,
- applied feedback from v1 (Octave script in git tree),
- added one more patch extracting common parts,
- rebased on mm-stable bbe832b9db2e.

Michal Koutný (5):
  selftests: memcg: Fix compilation
  selftests: memcg: Expect no low events in unprotected sibling
  selftests: memcg: Adjust expected reclaim values of protected cgroups
  selftests: memcg: Remove protection from top level memcg
  selftests: memcg: Factor out common parts of memory.{low,min} tests

 MAINTAINERS                                   |   1 +
 .../selftests/cgroup/memcg_protection.m       |  89 +++++++
 .../selftests/cgroup/test_memcontrol.c        | 247 +++++-------------
 3 files changed, 152 insertions(+), 185 deletions(-)
 create mode 100644 tools/testing/selftests/cgroup/memcg_protection.m

-- 
2.35.3

[PATCH v3 1/5] selftests: memcg: Fix compilation

[Michal Koutný]

This fixes mis-applied changes from commit 72b1e03aa725 ("cgroup:
account for memory_localevents in test_memcg_oom_group_leaf_events()").

Fixes: 72b1e03aa725 ("cgroup: account for memory_localevents in test_memcg_oom_group_leaf_events()")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: David Vernet <void@manifault.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
---
 .../selftests/cgroup/test_memcontrol.c        | 25 +++++++++++--------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index 6ab94317c87b..c012db9d07d6 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -1241,7 +1241,16 @@ static int test_memcg_oom_group_leaf_events(const char *root)
 	if (cg_read_key_long(child, "memory.events", "oom_kill ") <= 0)
 		goto cleanup;
 
-	if (cg_read_key_long(parent, "memory.events", "oom_kill ") <= 0)
+	parent_oom_events = cg_read_key_long(
+			parent, "memory.events", "oom_kill ");
+	/*
+	 * If memory_localevents is not enabled (the default), the parent should
+	 * count OOM events in its children groups. Otherwise, it should not
+	 * have observed any events.
+	 */
+	if (has_localevents && parent_oom_events != 0)
+		goto cleanup;
+	else if (!has_localevents && parent_oom_events <= 0)
 		goto cleanup;
 
 	ret = KSFT_PASS;
@@ -1349,20 +1358,14 @@ static int test_memcg_oom_group_score_events(const char *root)
 	if (!cg_run(memcg, alloc_anon, (void *)MB(100)))
 		goto cleanup;
 
-	parent_oom_events = cg_read_key_long(
-			parent, "memory.events", "oom_kill ");
-	/*
-	 * If memory_localevents is not enabled (the default), the parent should
-	 * count OOM events in its children groups. Otherwise, it should not
-	 * have observed any events.
-	 */
-	if ((has_localevents && parent_oom_events == 0) ||
-	     parent_oom_events > 0)
-		ret = KSFT_PASS;
+	if (cg_read_key_long(memcg, "memory.events", "oom_kill ") != 3)
+		goto cleanup;
 
 	if (kill(safe_pid, SIGKILL))
 		goto cleanup;
 
+	ret = KSFT_PASS;
+
 cleanup:
 	if (memcg)
 		cg_destroy(memcg);
-- 
2.35.3

[PATCH v3 2/5] selftests: memcg: Expect no low events in unprotected sibling

[Michal Koutný]

This is effectively a revert of commit cdc69458a5f3 ("cgroup: account
for memory_recursiveprot in test_memcg_low()"). The case test_memcg_low
will fail with memory_recursiveprot until resolved in reclaim
code.
However, this patch preserves the existing helpers and variables for
later uses.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: David Vernet <void@manifault.com>
---
 tools/testing/selftests/cgroup/test_memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index c012db9d07d6..4924425639b0 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -528,7 +528,7 @@ static int test_memcg_low(const char *root)
 	}
 
 	for (i = 0; i < ARRAY_SIZE(children); i++) {
-		int no_low_events_index = has_recursiveprot ? 2 : 1;
+		int no_low_events_index = 1;
 
 		oom = cg_read_key_long(children[i], "memory.events", "oom ");
 		low = cg_read_key_long(children[i], "memory.events", "low ");
-- 
2.35.3

[PATCH v3 3/5] selftests: memcg: Adjust expected reclaim values of protected cgroups

[Michal Koutný]

The numbers are not easy to derive in a closed form (certainly mere
protections ratios do not apply), therefore use a simulation to obtain
expected numbers.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
---
 MAINTAINERS                                   |  1 +
 .../selftests/cgroup/memcg_protection.m       | 89 +++++++++++++++++++
 .../selftests/cgroup/test_memcontrol.c        | 29 +++---
 3 files changed, 107 insertions(+), 12 deletions(-)
 create mode 100644 tools/testing/selftests/cgroup/memcg_protection.m

diff --git a/MAINTAINERS b/MAINTAINERS
index 78c57046fa93..b28b6aeb8636 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5029,6 +5029,7 @@ L:	linux-mm@kvack.org
 S:	Maintained
 F:	mm/memcontrol.c
 F:	mm/swap_cgroup.c
+F:	tools/testing/selftests/cgroup/memcg_protection.m
 F:	tools/testing/selftests/cgroup/test_kmem.c
 F:	tools/testing/selftests/cgroup/test_memcontrol.c
 
diff --git a/tools/testing/selftests/cgroup/memcg_protection.m b/tools/testing/selftests/cgroup/memcg_protection.m
new file mode 100644
index 000000000000..051daa3477b6
--- /dev/null
+++ b/tools/testing/selftests/cgroup/memcg_protection.m
@@ -0,0 +1,89 @@
+% SPDX-License-Identifier: GPL-2.0
+%
+% run as: octave-cli memcg_protection.m
+%
+% This script simulates reclaim protection behavior on a single level of memcg
+% hierarchy to illustrate how overcommitted protection spreads among siblings
+% (as it depends also on their current consumption).
+%
+% Simulation assumes siblings consumed the initial amount of memory (w/out
+% reclaim) and then the reclaim starts, all memory is reclaimable, i.e. treated
+% same. It simulates only non-low reclaim and assumes all memory.min = 0.
+%
+% Input configurations
+% --------------------
+% E number	parent effective protection
+% n vector	nominal protection of siblings set at the given level (memory.low)
+% c vector	current consumption -,,- (memory.current)
+
+% example from testcase (values in GB)
+E = 50 / 1024;
+n = [75 25 0 500 ] / 1024;
+c = [50 50 50 0] / 1024;
+
+% Reclaim parameters
+% ------------------
+
+% Minimal reclaim amount (GB)
+cluster = 32*4 / 2**20;
+
+% Reclaim coefficient (think as 0.5^sc->priority)
+alpha = .1
+
+% Simulation parameters
+% ---------------------
+epsilon = 1e-7;
+timeout = 1000;
+
+% Simulation loop
+% ---------------
+
+ch = [];
+eh = [];
+rh = [];
+
+for t = 1:timeout
+        % low_usage
+        u = min(c, n);
+        siblings = sum(u);
+
+        % effective_protection()
+        protected = min(n, c);                % start with nominal
+        e = protected * min(1, E / siblings); % normalize overcommit
+
+        % recursive protection
+        unclaimed = max(0, E - siblings);
+        parent_overuse = sum(c) - siblings;
+        if (unclaimed > 0 && parent_overuse > 0)
+                overuse = max(0, c - protected);
+                e += unclaimed * (overuse / parent_overuse);
+        endif
+
+        % get_scan_count()
+        r = alpha * c;             % assume all memory is in a single LRU list
+
+        % commit 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection")
+        sz = max(e, c);
+        r .*= (1 - (e+epsilon) ./ (sz+epsilon));
+
+        % uncomment to debug prints
+        % e, c, r
+
+        % nothing to reclaim, reached equilibrium
+        if max(r) < epsilon
+                break;
+        endif
+
+        % SWAP_CLUSTER_MAX roundup
+        r = max(r, (r > epsilon) .* cluster);
+        % XXX here I do parallel reclaim of all siblings
+        % in reality reclaim is serialized and each sibling recalculates own residual
+        c = max(c - r, 0);
+
+        ch = [ch ; c];
+        eh = [eh ; e];
+        rh = [rh ; r];
+endfor
+
+t
+c, e
diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index 4924425639b0..dc2c7d6e3572 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -248,7 +248,7 @@ static int cg_test_proc_killed(const char *cgroup)
 /*
  * First, this test creates the following hierarchy:
  * A       memory.min = 50M,  memory.max = 200M
- * A/B     memory.min = 50M,  memory.current = 50M
+ * A/B     memory.min = 50M
  * A/B/C   memory.min = 75M,  memory.current = 50M
  * A/B/D   memory.min = 25M,  memory.current = 50M
  * A/B/E   memory.min = 0,    memory.current = 50M
@@ -259,10 +259,13 @@ static int cg_test_proc_killed(const char *cgroup)
  * Then it creates A/G and creates a significant
  * memory pressure in it.
  *
+ * Then it checks actual memory usages and expects that:
  * A/B    memory.current ~= 50M
- * A/B/C  memory.current ~= 33M
- * A/B/D  memory.current ~= 17M
- * A/B/F  memory.current ~= 0
+ * A/B/C  memory.current ~= 29M
+ * A/B/D  memory.current ~= 21M
+ * A/B/E  memory.current ~= 0
+ * A/B/F  memory.current  = 0
+ * (for origin of the numbers, see model in memcg_protection.m.)
  *
  * After that it tries to allocate more than there is
  * unprotected memory in A available, and checks
@@ -365,10 +368,10 @@ static int test_memcg_min(const char *root)
 	for (i = 0; i < ARRAY_SIZE(children); i++)
 		c[i] = cg_read_long(children[i], "memory.current");
 
-	if (!values_close(c[0], MB(33), 10))
+	if (!values_close(c[0], MB(29), 10))
 		goto cleanup;
 
-	if (!values_close(c[1], MB(17), 10))
+	if (!values_close(c[1], MB(21), 10))
 		goto cleanup;
 
 	if (c[3] != 0)
@@ -405,7 +408,7 @@ static int test_memcg_min(const char *root)
 /*
  * First, this test creates the following hierarchy:
  * A       memory.low = 50M,  memory.max = 200M
- * A/B     memory.low = 50M,  memory.current = 50M
+ * A/B     memory.low = 50M
  * A/B/C   memory.low = 75M,  memory.current = 50M
  * A/B/D   memory.low = 25M,  memory.current = 50M
  * A/B/E   memory.low = 0,    memory.current = 50M
@@ -417,9 +420,11 @@ static int test_memcg_min(const char *root)
  *
  * Then it checks actual memory usages and expects that:
  * A/B    memory.current ~= 50M
- * A/B/   memory.current ~= 33M
- * A/B/D  memory.current ~= 17M
- * A/B/F  memory.current ~= 0
+ * A/B/C  memory.current ~= 29M
+ * A/B/D  memory.current ~= 21M
+ * A/B/E  memory.current ~= 0
+ * A/B/F  memory.current  = 0
+ * (for origin of the numbers, see model in memcg_protection.m.)
  *
  * After that it tries to allocate more than there is
  * unprotected memory in A available,
@@ -512,10 +517,10 @@ static int test_memcg_low(const char *root)
 	for (i = 0; i < ARRAY_SIZE(children); i++)
 		c[i] = cg_read_long(children[i], "memory.current");
 
-	if (!values_close(c[0], MB(33), 10))
+	if (!values_close(c[0], MB(29), 10))
 		goto cleanup;
 
-	if (!values_close(c[1], MB(17), 10))
+	if (!values_close(c[1], MB(21), 10))
 		goto cleanup;
 
 	if (c[3] != 0)
-- 
2.35.3

[PATCH v3 4/5] selftests: memcg: Remove protection from top level memcg

[Michal Koutný]

The reclaim is triggered by memory limit in a subtree, therefore the
testcase does not need configured protection against external reclaim.

Also, correct respective comments

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
---
 tools/testing/selftests/cgroup/test_memcontrol.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index dc2c7d6e3572..63c6a683a8c1 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -247,7 +247,7 @@ static int cg_test_proc_killed(const char *cgroup)
 
 /*
  * First, this test creates the following hierarchy:
- * A       memory.min = 50M,  memory.max = 200M
+ * A       memory.min = 0,    memory.max = 200M
  * A/B     memory.min = 50M
  * A/B/C   memory.min = 75M,  memory.current = 50M
  * A/B/D   memory.min = 25M,  memory.current = 50M
@@ -257,7 +257,7 @@ static int cg_test_proc_killed(const char *cgroup)
  * Usages are pagecache, but the test keeps a running
  * process in every leaf cgroup.
  * Then it creates A/G and creates a significant
- * memory pressure in it.
+ * memory pressure in A.
  *
  * Then it checks actual memory usages and expects that:
  * A/B    memory.current ~= 50M
@@ -338,8 +338,6 @@ static int test_memcg_min(const char *root)
 			      (void *)(long)fd);
 	}
 
-	if (cg_write(parent[0], "memory.min", "50M"))
-		goto cleanup;
 	if (cg_write(parent[1], "memory.min", "50M"))
 		goto cleanup;
 	if (cg_write(children[0], "memory.min", "75M"))
@@ -407,7 +405,7 @@ static int test_memcg_min(const char *root)
 
 /*
  * First, this test creates the following hierarchy:
- * A       memory.low = 50M,  memory.max = 200M
+ * A       memory.low = 0,    memory.max = 200M
  * A/B     memory.low = 50M
  * A/B/C   memory.low = 75M,  memory.current = 50M
  * A/B/D   memory.low = 25M,  memory.current = 50M
@@ -495,8 +493,6 @@ static int test_memcg_low(const char *root)
 			goto cleanup;
 	}
 
-	if (cg_write(parent[0], "memory.low", "50M"))
-		goto cleanup;
 	if (cg_write(parent[1], "memory.low", "50M"))
 		goto cleanup;
 	if (cg_write(children[0], "memory.low", "75M"))
-- 
2.35.3

Re: [PATCH v3 5/5] selftests: memcg: Factor out common parts of memory.{low,min} tests

[Roman Gushchin]

On Tue, May 24, 2022 at 06:29:55PM +0200, Michal Koutny wrote:
> The memory protection test setup and runtime is almost equal for
> memory.low and memory.min cases.
> It makes modification of the common parts prone to mistakes, since the
> protections are similar not only in setup but also in principle, factor
> the common part out.
> 
> Past exceptions between the tests:
> - missing memory.min is fine (kept),
> - test_memcg_low protected orphaned pagecache (adapted like
>   test_memcg_min and we keep the processes of protected memory running).
> 
> The evaluation in two tests is different (OOM of allocator vs low events
> of protégés), this is kept different.
> 
> Signed-off-by: Michal Koutný <mkoutny@suse.com>

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Re: [PATCH v3 2/5] selftests: memcg: Expect no low events in unprotected sibling

[Roman Gushchin]

On Tue, May 24, 2022 at 06:29:52PM +0200, Michal Koutny wrote:
> This is effectively a revert of commit cdc69458a5f3 ("cgroup: account
> for memory_recursiveprot in test_memcg_low()"). The case test_memcg_low
> will fail with memory_recursiveprot until resolved in reclaim
> code.
> However, this patch preserves the existing helpers and variables for
> later uses.
> 
> Signed-off-by: Michal Koutný <mkoutny@suse.com>
> Reviewed-by: David Vernet <void@manifault.com>

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>