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Mon, 14 Apr 2025 02:13:02 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.88.48]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 382B0180AF7C; Mon, 14 Apr 2025 02:12:58 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , =?utf-8?q?Michal_Koutn=C3=BD?= , Shuah Khan Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Waiman Long Subject: [PATCH v6 1/2] mm/vmscan: Skip memcg with !usage in shrink_node_memcgs() Date: Sun, 13 Apr 2025 22:12:48 -0400 Message-ID: <20250414021249.3232315-2-longman@redhat.com> In-Reply-To: <20250414021249.3232315-1-longman@redhat.com> References: <20250414021249.3232315-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E5B514000B X-Stat-Signature: g6sdgsr66o44ywgguzcuyow1nb7t7aid X-HE-Tag: 1744596786-535025 X-HE-Meta: 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 i46Kv1gX AY++aEs5El9mVVQDRrhxJqgiWVNMCebuzKUfcqwlcw6R/SyefQA7mgsA4qoIbJ+04Pk2RUCAoj9eA5cHLltvlRLtd+3vGfDzXYJ9nS9DOeMD52DYKaUIHVNsGbDFGpJtCYR5TECbj4Ne9ooNfJ8GGhg8upPwFCQVU3a+mObtRVgdpJS6Bexxm0nxCGAoicxrBycdJdnPKjhEV2UYrmIiT7lveSY4kyuLh39DJujHja9qdRJSNDgd5i+clBBEpSQrJowaoreEO3BNPcO8RbZN1H8iC3/cpTxUbT2fuSGl/GghM33qOCUVKs9GPGQ8EbyNRmTYRpNCYiLsLK/04AaW8MdlxUoBE14glr7w12IPndnFsBJxX8QaOTsyhpRQwQzH32nd3+XQX1vBBKZ/OBqThLF7xlyXrIqSQBBxy2yFt/xMfBITrwsaZ1UY4Mu3QBHXsFQa/2CANvDRrPL9BI9AmW5AqPSbY7HyZBeb1sOCpnvY9hkByIDoKmxYcDZIiVVAQ3iKY5IDuaH/xp+ZSVPliZ/E1E1/isFW5+1L+/wuIecQh4fohYaSTZNUksuTTLtx3WQ1BLEeyQHaNI6A= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The test_memcontrol selftest consistently fails its test_memcg_low sub-test due to the fact that two of its test child cgroups which have a memmory.low of 0 or an effective memory.low of 0 still have low events generated for them since mem_cgroup_below_low() use the ">=" operator when comparing to elow. The two failed use cases are as follows: 1) memory.low is set to 0, but low events can still be triggered and so the cgroup may have a non-zero low event count. 2) memory.low is set to a non-zero value but the cgroup has no task in it so that it has an effective low value of 0. Again it may have a non-zero low event count if memory reclaim happens. This is probably not a result expected by the users and it is really doubtful that users will check an empty cgroup with no task in it and expecting some non-zero event counts. In the first case, even though memory.low isn't set, it may still have some low protection if memory.low is set in the parent and the cgroup2 memory_recursiveprot mount option is enabled. So low event may still be recorded. The test_memcontrol.c test has to be modified to account for that. For the second case, it really doesn't make sense to have non-zero low event if the cgroup has 0 usage. So we need to skip this corner case in shrink_node_memcgs() by skipping the !usage case. With this patch applied, the test_memcg_low sub-test finishes successfully without failure in most cases. Though both test_memcg_low and test_memcg_min sub-tests may still fail occasionally if the memory.current values fall outside of the expected ranges. Suggested-by: Johannes Weiner Suggested-by: Michal Koutný Signed-off-by: Waiman Long --- mm/internal.h | 9 +++++++++ mm/memcontrol-v1.h | 2 -- mm/vmscan.c | 4 ++++ tools/testing/selftests/cgroup/test_memcontrol.c | 16 +++++++++++----- 4 files changed, 24 insertions(+), 7 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 50c2f590b2d0..c06fb0e8d75c 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1535,6 +1535,15 @@ void __meminit __init_page_from_nid(unsigned long pfn, int nid); unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg, int priority); +#ifdef CONFIG_MEMCG +unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap); +#else +static inline unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) +{ + return 1UL; +} +#endif + #ifdef CONFIG_SHRINKER_DEBUG static inline __printf(2, 0) int shrinker_debugfs_name_alloc( struct shrinker *shrinker, const char *fmt, va_list ap) diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h index 6358464bb416..e92b21af92b1 100644 --- a/mm/memcontrol-v1.h +++ b/mm/memcontrol-v1.h @@ -22,8 +22,6 @@ iter != NULL; \ iter = mem_cgroup_iter(NULL, iter, NULL)) -unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap); - void drain_all_stock(struct mem_cgroup *root_memcg); unsigned long memcg_events(struct mem_cgroup *memcg, int event); diff --git a/mm/vmscan.c b/mm/vmscan.c index b620d74b0f66..a771a0145a12 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5963,6 +5963,10 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) mem_cgroup_calculate_protection(target_memcg, memcg); + /* Skip memcg with no usage */ + if (!mem_cgroup_usage(memcg, false)) + continue; + if (mem_cgroup_below_min(target_memcg, memcg)) { /* * Hard protection. diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 16f5d74ae762..5a5dcbe57b56 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -380,10 +380,10 @@ static bool reclaim_until(const char *memcg, long goal); * * Then it checks actual memory usages and expects that: * A/B memory.current ~= 50M - * A/B/C memory.current ~= 29M - * A/B/D memory.current ~= 21M - * A/B/E memory.current ~= 0 - * A/B/F memory.current = 0 + * A/B/C memory.current ~= 29M [memory.events:low > 0] + * A/B/D memory.current ~= 21M [memory.events:low > 0] + * A/B/E memory.current ~= 0 [memory.events:low == 0 if !memory_recursiveprot, > 0 otherwise] + * A/B/F memory.current = 0 [memory.events:low == 0] * (for origin of the numbers, see model in memcg_protection.m.) * * After that it tries to allocate more than there is @@ -525,8 +525,14 @@ static int test_memcg_protection(const char *root, bool min) goto cleanup; } + /* + * Child 2 has memory.low=0, but some low protection is still being + * distributed down from its parent with memory.low=50M if cgroup2 + * memory_recursiveprot mount option is enabled. So the low event + * count will be non-zero in this case. + */ for (i = 0; i < ARRAY_SIZE(children); i++) { - int no_low_events_index = 1; + int no_low_events_index = has_recursiveprot ? 2 : 1; long low, oom; oom = cg_read_key_long(children[i], "memory.events", "oom ");