On Mon, Apr 12, 2021 at 4:10 PM Shakeel Butt <shake...@google.com> wrote: > > On Mon, Apr 12, 2021 at 3:55 PM Waiman Long <long...@redhat.com> wrote: > > > > Most kmem_cache_alloc() calls are from user context. With instrumentation > > enabled, the measured amount of kmem_cache_alloc() calls from non-task > > context was about 0.01% of the total. > > > > The irq disable/enable sequence used in this case to access content > > from object stock is slow. To optimize for user context access, there > > are now two object stocks for task context and interrupt context access > > respectively. > > > > The task context object stock can be accessed after disabling preemption > > which is cheap in non-preempt kernel. The interrupt context object stock > > can only be accessed after disabling interrupt. User context code can > > access interrupt object stock, but not vice versa. > > > > The mod_objcg_state() function is also modified to make sure that memcg > > and lruvec stat updates are done with interrupted disabled. > > > > The downside of this change is that there are more data stored in local > > object stocks and not reflected in the charge counter and the vmstat > > arrays. However, this is a small price to pay for better performance. > > > > Signed-off-by: Waiman Long <long...@redhat.com> > > Acked-by: Roman Gushchin <g...@fb.com> > > --- > > mm/memcontrol.c | 73 +++++++++++++++++++++++++++++++++++++++---------- > > 1 file changed, 59 insertions(+), 14 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 69f728383efe..29f2df76644a 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2229,7 +2229,8 @@ struct obj_stock { > > struct memcg_stock_pcp { > > struct mem_cgroup *cached; /* this never be root cgroup */ > > unsigned int nr_pages; > > - struct obj_stock obj; > > + struct obj_stock task_obj; > > + struct obj_stock irq_obj; > > > > struct work_struct work; > > unsigned long flags; > > @@ -2254,11 +2255,48 @@ static bool obj_stock_flush_required(struct > > memcg_stock_pcp *stock, > > } > > #endif > > > > +/* > > + * Most kmem_cache_alloc() calls are from user context. The irq > > disable/enable > > + * sequence used in this case to access content from object stock is slow. > > + * To optimize for user context access, there are now two object stocks for > > + * task context and interrupt context access respectively. > > + * > > + * The task context object stock can be accessed by disabling preemption > > only > > + * which is cheap in non-preempt kernel. The interrupt context object stock > > + * can only be accessed after disabling interrupt. User context code can > > + * access interrupt object stock, but not vice versa. > > + */ > > static inline struct obj_stock *current_obj_stock(void) > > { > > struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock); > > > > - return &stock->obj; > > + return in_task() ? &stock->task_obj : &stock->irq_obj; > > +} > > + > > +#define get_obj_stock(flags) \ > > +({ \ > > + struct memcg_stock_pcp *stock; \ > > + struct obj_stock *obj_stock; \ > > + \ > > + if (in_task()) { \ > > + preempt_disable(); \ > > + (flags) = -1L; \ > > + stock = this_cpu_ptr(&memcg_stock); \ > > The above line was missing in the previous version. > > > + obj_stock = &stock->task_obj; \ > > + } else { \ > > + local_irq_save(flags); \ > > + stock = this_cpu_ptr(&memcg_stock); \ > > + obj_stock = &stock->irq_obj; \ > > + } \ > > + obj_stock; \ > > +}) > > + > > +static inline void put_obj_stock(unsigned long flags) > > +{ > > + if (flags == -1L) > > + preempt_enable(); > > + else > > + local_irq_restore(flags); > > } > > > > /** > > @@ -2327,7 +2365,9 @@ static void drain_local_stock(struct work_struct > > *dummy) > > local_irq_save(flags); > > > > stock = this_cpu_ptr(&memcg_stock); > > - drain_obj_stock(&stock->obj); > > + drain_obj_stock(&stock->irq_obj); > > + if (in_task()) > > + drain_obj_stock(&stock->task_obj); > > drain_stock(stock); > > clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); > > > > @@ -3183,7 +3223,7 @@ static inline void mod_objcg_state(struct obj_cgroup > > *objcg, > > memcg = obj_cgroup_memcg(objcg); > > if (pgdat) > > lruvec = mem_cgroup_lruvec(memcg, pgdat); > > - __mod_memcg_lruvec_state(memcg, lruvec, idx, nr); > > + mod_memcg_lruvec_state(memcg, lruvec, idx, nr); > > rcu_read_unlock(); > > } > > > > @@ -3193,7 +3233,7 @@ static bool consume_obj_stock(struct obj_cgroup > > *objcg, unsigned int nr_bytes) > > unsigned long flags; > > bool ret = false; > > > > - local_irq_save(flags); > > + stock = get_obj_stock(flags); > > > > stock = current_obj_stock(); > > The above is redundant. >
After cleanup you can add: Reviewed-by: Shakeel Butt <shake...@google.com>