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mm: memcontrol: take a css reference for each charged page

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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 <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2014-12-10 15:42:42 -08:00 committed by Linus Torvalds
parent 5ac8fb31ad
commit e8ea14cc6e
3 changed files with 92 additions and 24 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

26
include/linux/cgroup.h
View file

@ -112,6 +112,19 @@ static inline void css_get(struct cgroup_subsys_state *css)
percpu_ref_get(&css->refcnt);
}
/**
* 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 {
/* Control Group requires release notifications to userspace */

69
include/linux/percpu-refcount.h
View file

@ -146,6 +146,29 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref,
return true;
}
/**
* percpu_ref_get_many - increment a percpu refcount
* @ref: percpu_ref to get
* @nr: number of references to get
*
* Analogous to atomic_long_add().
*
* This function is safe to call as long as @ref is between init and exit.
*/
static inline void percpu_ref_get_many(struct percpu_ref *ref, unsigned long nr)
{
unsigned long __percpu *percpu_count;
rcu_read_lock_sched();
if (__ref_is_percpu(ref, &percpu_count))
this_cpu_add(*percpu_count, nr);
else
atomic_long_add(nr, &ref->count);
rcu_read_unlock_sched();
}
/**
* percpu_ref_get - increment a percpu refcount
* @ref: percpu_ref to get
@ -156,16 +179,7 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref,
*/
static inline void percpu_ref_get(struct percpu_ref *ref)
{
unsigned long __percpu *percpu_count;
rcu_read_lock_sched();
if (__ref_is_percpu(ref, &percpu_count))
this_cpu_inc(*percpu_count);
else
atomic_long_inc(&ref->count);
rcu_read_unlock_sched();
percpu_ref_get_many(ref, 1);
}
/**
@ -230,6 +244,30 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
return ret;
}
/**
* 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())
*
* This function is safe to call as long as @ref is between init and exit.
*/
static inline void percpu_ref_put_many(struct percpu_ref *ref, unsigned long nr)
{
unsigned long __percpu *percpu_count;
rcu_read_lock_sched();
if (__ref_is_percpu(ref, &percpu_count))
this_cpu_sub(*percpu_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
@ -241,16 +279,7 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
*/
static inline void percpu_ref_put(struct percpu_ref *ref)
{
unsigned long __percpu *percpu_count;
rcu_read_lock_sched();
if (__ref_is_percpu(ref, &percpu_count))
this_cpu_dec(*percpu_count);
else if (unlikely(atomic_long_dec_and_test(&ref->count)))
ref->release(ref);
rcu_read_unlock_sched();
percpu_ref_put_many(ref, 1);
}
/**

21
mm/memcontrol.c
View file

@ -2273,6 +2273,7 @@ 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;
@ -2530,6 +2531,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
return -EINTR;
done_restock:
css_get_many(&memcg->css, batch);
if (batch > nr_pages)
refill_stock(memcg, batch - nr_pages);
done:
@ -2544,6 +2546,8 @@ 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);
}
/*
@ -2739,6 +2743,7 @@ static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp,
page_counter_charge(&memcg->memory, nr_pages);
if (do_swap_account)
page_counter_charge(&memcg->memsw, nr_pages);
css_get_many(&memcg->css, nr_pages);
ret = 0;
} else if (ret)
page_counter_uncharge(&memcg->kmem, nr_pages);
@ -2754,8 +2759,10 @@ 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
@ -2767,6 +2774,8 @@ 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);
}
/*
@ -3394,10 +3403,13 @@ 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)
@ -5767,7 +5779,6 @@ static void __mem_cgroup_clear_mc(void)
{
struct mem_cgroup *from = mc.from;
struct mem_cgroup *to = mc.to;
int i;
/* we must uncharge all the leftover precharges from mc.to */
if (mc.precharge) {
@ -5795,8 +5806,7 @@ static void __mem_cgroup_clear_mc(void)
if (!mem_cgroup_is_root(mc.to))
page_counter_uncharge(&mc.to->memory, mc.moved_swap);
for (i = 0; i < mc.moved_swap; i++)
css_put(&mc.from->css);
css_put_many(&mc.from->css, mc.moved_swap);
/* we've already done css_get(mc.to) */
mc.moved_swap = 0;
@ -6343,6 +6353,9 @@ 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)