Charges currently pin the css indirectly by playing tricks during css_offline(): user pages stall the offlining process until all of them have been reparented, whereas kmemcg acquires a keep-alive reference if outstanding kernel pages are detected at that point.
In preparation for removing all this complexity, make the pinning explicit and acquire a css references for every charged page. Signed-off-by: Johannes Weiner <[email protected]> --- include/linux/cgroup.h | 26 +++++++++++++++++++++++++ include/linux/percpu-refcount.h | 43 ++++++++++++++++++++++++++++++++--------- mm/memcontrol.c | 17 +++++++++++++++- 3 files changed, 76 insertions(+), 10 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index b5223c570eba..a9fe70d9c7c5 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -113,6 +113,19 @@ static inline void css_get(struct cgroup_subsys_state *css) } /** + * css_get_many - obtain references on the specified css + * @css: target css + * @n: number of references to get + * + * The caller must already have a reference. + */ +static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_get_many(&css->refcnt, n); +} + +/** * css_tryget - try to obtain a reference on the specified css * @css: target css * @@ -159,6 +172,19 @@ static inline void css_put(struct cgroup_subsys_state *css) percpu_ref_put(&css->refcnt); } +/** + * css_put_many - put css references + * @css: target css + * @n: number of references to put + * + * Put references obtained via css_get() and css_tryget_online(). + */ +static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_put_many(&css->refcnt, n); +} + /* bits in struct cgroup flags field */ enum { /* diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index b1973ba1d5f3..a4551456e06f 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -112,26 +112,38 @@ static inline bool __pcpu_ref_alive(struct percpu_ref *ref, } /** - * percpu_ref_get - increment a percpu refcount + * percpu_ref_get_many - increment a percpu refcount * @ref: percpu_ref to get + * @nr: number of references to get * - * Analagous to atomic_inc(). + * Analagous to atomic_add(). */ -static inline void percpu_ref_get(struct percpu_ref *ref) +static inline void percpu_ref_get_many(struct percpu_ref *ref, unsigned long nr) { unsigned long __percpu *pcpu_count; rcu_read_lock_sched(); if (__pcpu_ref_alive(ref, &pcpu_count)) - this_cpu_inc(*pcpu_count); + this_cpu_add(*pcpu_count, nr); else - atomic_long_inc(&ref->count); + atomic_long_add(nr, &ref->count); rcu_read_unlock_sched(); } /** + * percpu_ref_get - increment a percpu refcount + * @ref: percpu_ref to get + * + * Analagous to atomic_inc(). + */ +static inline void percpu_ref_get(struct percpu_ref *ref) +{ + percpu_ref_get_many(ref, 1); +} + +/** * percpu_ref_tryget - try to increment a percpu refcount * @ref: percpu_ref to try-get * @@ -191,27 +203,40 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref) } /** - * percpu_ref_put - decrement a percpu refcount + * percpu_ref_put_many - decrement a percpu refcount * @ref: percpu_ref to put + * @nr: number of references to put * * Decrement the refcount, and if 0, call the release function (which was passed * to percpu_ref_init()) */ -static inline void percpu_ref_put(struct percpu_ref *ref) +static inline void percpu_ref_put_many(struct percpu_ref *ref, unsigned long nr) { unsigned long __percpu *pcpu_count; rcu_read_lock_sched(); if (__pcpu_ref_alive(ref, &pcpu_count)) - this_cpu_dec(*pcpu_count); - else if (unlikely(atomic_long_dec_and_test(&ref->count))) + this_cpu_sub(*pcpu_count, nr); + else if (unlikely(atomic_long_sub_and_test(nr, &ref->count))) ref->release(ref); rcu_read_unlock_sched(); } /** + * percpu_ref_put - decrement a percpu refcount + * @ref: percpu_ref to put + * + * Decrement the refcount, and if 0, call the release function (which was passed + * to percpu_ref_init()) + */ +static inline void percpu_ref_put(struct percpu_ref *ref) +{ + percpu_ref_put_many(ref, 1); +} + +/** * percpu_ref_is_zero - test whether a percpu refcount reached zero * @ref: percpu_ref to test * diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 154161bb7d4c..b832c87ec43b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2317,6 +2317,7 @@ static void drain_stock(struct memcg_stock_pcp *stock) page_counter_uncharge(&old->memory, stock->nr_pages); if (do_swap_account) page_counter_uncharge(&old->memsw, stock->nr_pages); + css_put_many(&old->css, stock->nr_pages); stock->nr_pages = 0; } stock->cached = NULL; @@ -2573,6 +2574,7 @@ bypass: return -EINTR; done_restock: + css_get_many(&memcg->css, batch); if (batch > nr_pages) refill_stock(memcg, batch - nr_pages); done: @@ -2587,6 +2589,8 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) page_counter_uncharge(&memcg->memory, nr_pages); if (do_swap_account) page_counter_uncharge(&memcg->memsw, nr_pages); + + css_put_many(&memcg->css, nr_pages); } /* @@ -2788,6 +2792,7 @@ static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, page_counter_charge(&memcg->memory, nr_pages, NULL); if (do_swap_account) page_counter_charge(&memcg->memsw, nr_pages, NULL); + css_get_many(&memcg->css, nr_pages); ret = 0; } else if (ret) page_counter_uncharge(&memcg->kmem, nr_pages); @@ -2803,8 +2808,10 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg, page_counter_uncharge(&memcg->memsw, nr_pages); /* Not down to 0 */ - if (page_counter_uncharge(&memcg->kmem, nr_pages)) + if (page_counter_uncharge(&memcg->kmem, nr_pages)) { + css_put_many(&memcg->css, nr_pages); return; + } /* * Releases a reference taken in kmem_cgroup_css_offline in case @@ -2816,6 +2823,8 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg, */ if (memcg_kmem_test_and_clear_dead(memcg)) css_put(&memcg->css); + + css_put_many(&memcg->css, nr_pages); } /* @@ -3444,10 +3453,13 @@ static int mem_cgroup_move_parent(struct page *page, ret = mem_cgroup_move_account(page, nr_pages, pc, child, parent); if (!ret) { + if (!mem_cgroup_is_root(parent)) + css_get_many(&parent->css, nr_pages); /* Take charge off the local counters */ page_counter_cancel(&child->memory, nr_pages); if (do_swap_account) page_counter_cancel(&child->memsw, nr_pages); + css_put_many(&child->css, nr_pages); } if (nr_pages > 1) @@ -6379,6 +6391,9 @@ static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout, __this_cpu_add(memcg->stat->nr_page_events, nr_anon + nr_file); memcg_check_events(memcg, dummy_page); local_irq_restore(flags); + + if (!mem_cgroup_is_root(memcg)) + css_put_many(&memcg->css, max(nr_mem, nr_memsw)); } static void uncharge_list(struct list_head *page_list) -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
