From 4e97d64c492e1f65b4f7d14803ed580b279aaf6f Mon Sep 17 00:00:00 2001 From: Joshua Hahn Date: Wed, 11 Dec 2024 12:39:49 -0800 Subject: [PATCH] memcg/hugetlb: introduce memcg_accounts_hugetlb Patch series "memcg/hugetlb: Rework memcg hugetlb charging", v3. This series cleans up memcg's hugetlb charging logic by deprecating the current memcg hugetlb try-charge + {commit, cancel} logic present in alloc_hugetlb_folio. A single function mem_cgroup_charge_hugetlb takes its place instead. This makes the code more maintainable by simplifying the error path and reduces memcg's footprint in hugetlb logic. This patch introduces a few changes in the hugetlb folio allocation error path: (a) Instead of having multiple return points, we consolidate them to two: one for reaching the memcg limit or running out of memory (-ENOMEM) and one for hugetlb allocation fails / limit being reached (-ENOSPC). (b) Previously, the memcg limit was checked before the folio is acquired, meaning the hugeTLB folio isn't acquired if the limit is reached. This patch performs the charging after the folio is reached, meaning if memcg's limit is reached, the acquired folio is freed right away. This patch builds on two earlier patch series: [2] which adds memcg hugeTLB counters, and [3] which deprecates charge moving and removes the last references to mem_cgroup_cancel_charge. The request for this cleanup can be found in [2]. [1] https://lore.kernel.org/all/20231006184629.155543-1-nphamcs@gmail.com/ [2] https://lore.kernel.org/all/20241101204402.1885383-1-joshua.hahnjy@gmail.com/ [3] https://lore.kernel.org/linux-mm/20241025012304.2473312-1-shakeel.butt@linux.dev/ This patch (of 3): This patch isolates the check for whether memcg accounts hugetlb. This condition can only be true if the memcg mount option memory_hugetlb_accounting is on, which includes hugetlb usage in memory.current. Link: https://lkml.kernel.org/r/20241211203951.764733-1-joshua.hahnjy@gmail.com Link: https://lkml.kernel.org/r/20241211203951.764733-2-joshua.hahnjy@gmail.com Signed-off-by: Joshua Hahn Acked-by: Shakeel Butt Reviewed-by: Nhat Pham Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Muchun Song Signed-off-by: Andrew Morton --- mm/memcontrol.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 7b3503d12aaf1..b25eab9c933e8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1448,6 +1448,18 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item) memcg_page_state_output_unit(item); } +#ifdef CONFIG_HUGETLB_PAGE +static bool memcg_accounts_hugetlb(void) +{ + return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING; +} +#else /* CONFIG_HUGETLB_PAGE */ +static bool memcg_accounts_hugetlb(void) +{ + return false; +} +#endif /* CONFIG_HUGETLB_PAGE */ + static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) { int i; @@ -1469,7 +1481,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) #ifdef CONFIG_HUGETLB_PAGE if (unlikely(memory_stats[i].idx == NR_HUGETLB) && - !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)) + !memcg_accounts_hugetlb()) continue; #endif size = memcg_page_state_output(memcg, memory_stats[i].idx); @@ -4540,8 +4552,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp, * but do not attempt to commit charge later (or cancel on error) either. */ if (mem_cgroup_disabled() || !memcg || - !cgroup_subsys_on_dfl(memory_cgrp_subsys) || - !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)) + !cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb()) return -EOPNOTSUPP; if (try_charge(memcg, gfp, nr_pages)) -- 2.47.2