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Thu, 23 Apr 2026 13:34:57 -0700 (PDT) From: Joshua Hahn To: linux-mm@kvack.org Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton , Muchun Song , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [RFC PATCH 7/9 v2] mm/memcontrol: Make memory.low and memory.min tier-aware Date: Thu, 23 Apr 2026 13:34:41 -0700 Message-ID: <20260423203445.2914963-8-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260423203445.2914963-1-joshua.hahnjy@gmail.com> References: <20260423203445.2914963-1-joshua.hahnjy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On machines serving multiple workloads whose memory is isolated via the memory cgroup controller, it is currently impossible to enforce a fair distribution of toptier memory among the workloads, as the only enforceable limits have to do with total memory footprint, but not where that memory resides. This makes ensuring a consistent and baseline performance difficult, as each workload's performance is heavily impacted by workload-external factors such as which other workloads are co-located in the same host, and the order at which different workloads are started. Extend the existing memory.{low, min} protection to be tier-aware in order to enforce proportional best-effort and guaranteed memory protection of toptier memory. Signed-off-by: Joshua Hahn --- include/linux/memcontrol.h | 8 ++++++++ mm/memcontrol.c | 3 +++ 2 files changed, 11 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 6bcb866440075..2222b390ebf10 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -624,6 +624,10 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup *target, if (mem_cgroup_unprotected(target, memcg)) return false; + if (mem_cgroup_tiered_limits() && READ_ONCE(memcg->toptier.elow) >= + page_counter_read(&memcg->toptier)) + return true; + return READ_ONCE(memcg->memory.elow) >= page_counter_read(&memcg->memory); } @@ -634,6 +638,10 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup *target, if (mem_cgroup_unprotected(target, memcg)) return false; + if (mem_cgroup_tiered_limits() && READ_ONCE(memcg->toptier.emin) >= + page_counter_read(&memcg->toptier)) + return true; + return READ_ONCE(memcg->memory.emin) >= page_counter_read(&memcg->memory); } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3fb1ee1d18603..b115ff40e268d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4933,6 +4933,9 @@ void mem_cgroup_calculate_protection(struct mem_cgroup *root, root = root_mem_cgroup; page_counter_calculate_protection(&root->memory, &memcg->memory, recursive_protection); + if (mem_cgroup_tiered_limits()) + page_counter_calculate_protection(&root->toptier, + &memcg->toptier, recursive_protection); } static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg, -- 2.52.0