[RFC PATCH 3/3] mm/memcg: Allow the task_obj optimization only on non-PREEMPTIBLE kernels.
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: 2021-12-22 11:41:23
Also in:
cgroups
Subsystem:
control group - memory resource controller (memcg), memory management, the rest · Maintainers:
Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt, Andrew Morton, Linus Torvalds
Based on my understanding the optimisation with task_obj for in_task() mask sense on non-PREEMPTIBLE kernels because preempt_disable()/enable() is optimized away. This could be then restricted to !CONFIG_PREEMPTION kernel instead to only PREEMPT_RT. With CONFIG_PREEMPT_DYNAMIC a non-PREEMPTIBLE kernel can also be configured but these kernels always have preempt_disable()/enable() present so it probably makes no sense here for the optimisation. Restrict the optimisation to !CONFIG_PREEMPTION kernels. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- mm/memcontrol.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1e76f26be2c15..92180f1aa9edc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c@@ -2126,7 +2126,7 @@ struct memcg_stock_pcp { local_lock_t stock_lock; struct mem_cgroup *cached; /* this never be root cgroup */ unsigned int nr_pages; -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION /* Protects only task_obj */ local_lock_t task_obj_lock; struct obj_stock task_obj;
@@ -2139,7 +2139,7 @@ struct memcg_stock_pcp { }; static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = { .stock_lock = INIT_LOCAL_LOCK(stock_lock), -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION .task_obj_lock = INIT_LOCAL_LOCK(task_obj_lock), #endif };
@@ -2228,7 +2228,7 @@ static void drain_local_stock(struct work_struct *dummy) * drain_stock races is that we always operate on local CPU stock * here with IRQ disabled */ -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION local_lock(&memcg_stock.task_obj_lock); old = drain_obj_stock(&this_cpu_ptr(&memcg_stock)->task_obj, NULL); local_unlock(&memcg_stock.task_obj_lock);
@@ -2837,7 +2837,7 @@ static inline struct obj_stock *get_obj_stock(unsigned long *pflags, { struct memcg_stock_pcp *stock; -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION if (likely(in_task())) { *pflags = 0UL; *stock_pcp = NULL;
@@ -2855,7 +2855,7 @@ static inline struct obj_stock *get_obj_stock(unsigned long *pflags, static inline void put_obj_stock(unsigned long flags, struct memcg_stock_pcp *stock_pcp) { -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION if (likely(!stock_pcp)) local_unlock(&memcg_stock.task_obj_lock); else
@@ -3267,7 +3267,7 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, { struct mem_cgroup *memcg; -#ifndef CONFIG_PREEMPT_RT +#ifndef CONFIG_PREEMPTION if (in_task() && stock->task_obj.cached_objcg) { memcg = obj_cgroup_memcg(stock->task_obj.cached_objcg); if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
--
2.34.1