when reclaim memory, shink_slab will take lots of time even if
no memory is reclaimed, since list_lru_count_one called by it
needs to take a spinlock
try to optimize it by replacing spinlock with RCU in
__list_lru_count_one
$dd if=aaa of=bbb bs=1k count=3886080
$rm -f bbb
$time echo 100000000 >/cgroup/memory/test/memory.limit_in_bytes
Before: 0m0.415s ===> after: 0m0.395s
Signed-off-by: Li RongQing <[email protected]>
---
include/linux/list_lru.h | 2 ++
mm/list_lru.c | 69 ++++++++++++++++++++++++++++++++++--------------
2 files changed, 51 insertions(+), 20 deletions(-)
diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index bb8129a3474d..ae472538038e 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -29,6 +29,7 @@ struct list_lru_one {
struct list_head list;
/* may become negative during memcg reparenting */
long nr_items;
+ struct rcu_head rcu;
};
struct list_lru_memcg {
@@ -46,6 +47,7 @@ struct list_lru_node {
struct list_lru_memcg *memcg_lrus;
#endif
long nr_items;
+ struct rcu_head rcu;
} ____cacheline_aligned_in_smp;
struct list_lru {
diff --git a/mm/list_lru.c b/mm/list_lru.c
index fd41e969ede5..4c58ed861729 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -52,13 +52,13 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)
static inline struct list_lru_one *
list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
{
- /*
- * The lock protects the array of per cgroup lists from relocation
- * (see memcg_update_list_lru_node).
- */
- lockdep_assert_held(&nlru->lock);
- if (nlru->memcg_lrus && idx >= 0)
- return nlru->memcg_lrus->lru[idx];
+ struct list_lru_memcg *tmp;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ tmp = rcu_dereference(nlru->memcg_lrus);
+ if (tmp && idx >= 0)
+ return rcu_dereference(tmp->lru[idx]);
return &nlru->lru;
}
@@ -113,14 +113,17 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
struct list_lru_one *l;
spin_lock(&nlru->lock);
+ rcu_read_lock();
if (list_empty(item)) {
l = list_lru_from_kmem(nlru, item);
list_add_tail(item, &l->list);
l->nr_items++;
nlru->nr_items++;
+ rcu_read_unlock();
spin_unlock(&nlru->lock);
return true;
}
+ rcu_read_unlock();
spin_unlock(&nlru->lock);
return false;
}
@@ -133,14 +136,17 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
struct list_lru_one *l;
spin_lock(&nlru->lock);
+ rcu_read_lock();
if (!list_empty(item)) {
l = list_lru_from_kmem(nlru, item);
list_del_init(item);
l->nr_items--;
nlru->nr_items--;
+ rcu_read_unlock();
spin_unlock(&nlru->lock);
return true;
}
+ rcu_read_unlock();
spin_unlock(&nlru->lock);
return false;
}
@@ -166,12 +172,13 @@ static unsigned long __list_lru_count_one(struct list_lru *lru,
{
struct list_lru_node *nlru = &lru->node[nid];
struct list_lru_one *l;
- unsigned long count;
+ unsigned long count = 0;
- spin_lock(&nlru->lock);
+ rcu_read_lock();
l = list_lru_from_memcg_idx(nlru, memcg_idx);
- count = l->nr_items;
- spin_unlock(&nlru->lock);
+ if (l)
+ count = l->nr_items;
+ rcu_read_unlock();
return count;
}
@@ -204,6 +211,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
unsigned long isolated = 0;
spin_lock(&nlru->lock);
+ rcu_read_lock();
l = list_lru_from_memcg_idx(nlru, memcg_idx);
restart:
list_for_each_safe(item, n, &l->list) {
@@ -250,6 +258,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
}
}
+ rcu_read_unlock();
spin_unlock(&nlru->lock);
return isolated;
}
@@ -296,9 +305,14 @@ static void __memcg_destroy_list_lru_node(struct list_lru_memcg *memcg_lrus,
int begin, int end)
{
int i;
+ struct list_lru_one *tmp;
- for (i = begin; i < end; i++)
- kfree(memcg_lrus->lru[i]);
+ for (i = begin; i < end; i++) {
+ tmp = memcg_lrus->lru[i];
+ rcu_assign_pointer(memcg_lrus->lru[i], NULL);
+ if (tmp)
+ kfree_rcu(tmp, rcu);
+ }
}
static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
@@ -314,7 +328,7 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
goto fail;
init_one_lru(l);
- memcg_lrus->lru[i] = l;
+ rcu_assign_pointer(memcg_lrus->lru[i], l);
}
return 0;
fail:
@@ -325,25 +339,37 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
static int memcg_init_list_lru_node(struct list_lru_node *nlru)
{
int size = memcg_nr_cache_ids;
+ struct list_lru_memcg *tmp;
- nlru->memcg_lrus = kvmalloc(size * sizeof(void *), GFP_KERNEL);
- if (!nlru->memcg_lrus)
+ tmp = kvmalloc(size * sizeof(void *), GFP_KERNEL);
+ if (!tmp)
return -ENOMEM;
- if (__memcg_init_list_lru_node(nlru->memcg_lrus, 0, size)) {
- kvfree(nlru->memcg_lrus);
+ if (__memcg_init_list_lru_node(tmp, 0, size)) {
+ kvfree(tmp);
return -ENOMEM;
}
+ rcu_assign_pointer(nlru->memcg_lrus, tmp);
+
return 0;
}
-static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
+static void memcg_destroy_list_lru_node_rcu(struct rcu_head *rcu)
{
+ struct list_lru_node *nlru;
+
+ nlru = container_of(rcu, struct list_lru_node, rcu);
+
__memcg_destroy_list_lru_node(nlru->memcg_lrus, 0, memcg_nr_cache_ids);
kvfree(nlru->memcg_lrus);
}
+static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
+{
+ call_rcu(&nlru->rcu, memcg_destroy_list_lru_node_rcu);
+}
+
static int memcg_update_list_lru_node(struct list_lru_node *nlru,
int old_size, int new_size)
{
@@ -371,9 +397,10 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
* we have to use IRQ-safe primitives here to avoid deadlock.
*/
spin_lock_irq(&nlru->lock);
- nlru->memcg_lrus = new;
+ rcu_assign_pointer(nlru->memcg_lrus, new);
spin_unlock_irq(&nlru->lock);
+ synchronize_rcu();
kvfree(old);
return 0;
}
@@ -487,6 +514,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
* we have to use IRQ-safe primitives here to avoid deadlock.
*/
spin_lock_irq(&nlru->lock);
+ rcu_read_lock();
src = list_lru_from_memcg_idx(nlru, src_idx);
dst = list_lru_from_memcg_idx(nlru, dst_idx);
@@ -495,6 +523,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
dst->nr_items += src->nr_items;
src->nr_items = 0;
+ rcu_read_unlock();
spin_unlock_irq(&nlru->lock);
}
--
2.11.0
[CC Dave]
On Tue 27-03-18 15:59:04, Li RongQing wrote:
> when reclaim memory, shink_slab will take lots of time even if
> no memory is reclaimed, since list_lru_count_one called by it
> needs to take a spinlock
>
> try to optimize it by replacing spinlock with RCU in
> __list_lru_count_one
Isn't the RCU overkill here? Why cannot we simply do an optimistic
lockless check for nr_items? It would be racy but does it actually
matter? We should be able to tolerate occasional 0 to non-zero and vice
versa transitions AFAICS.
>
> $dd if=aaa of=bbb bs=1k count=3886080
> $rm -f bbb
> $time echo 100000000 >/cgroup/memory/test/memory.limit_in_bytes
>
> Before: 0m0.415s ===> after: 0m0.395s
>
> Signed-off-by: Li RongQing <[email protected]>
> ---
> include/linux/list_lru.h | 2 ++
> mm/list_lru.c | 69 ++++++++++++++++++++++++++++++++++--------------
> 2 files changed, 51 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> index bb8129a3474d..ae472538038e 100644
> --- a/include/linux/list_lru.h
> +++ b/include/linux/list_lru.h
> @@ -29,6 +29,7 @@ struct list_lru_one {
> struct list_head list;
> /* may become negative during memcg reparenting */
> long nr_items;
> + struct rcu_head rcu;
> };
>
> struct list_lru_memcg {
> @@ -46,6 +47,7 @@ struct list_lru_node {
> struct list_lru_memcg *memcg_lrus;
> #endif
> long nr_items;
> + struct rcu_head rcu;
> } ____cacheline_aligned_in_smp;
>
> struct list_lru {
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index fd41e969ede5..4c58ed861729 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -52,13 +52,13 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)
> static inline struct list_lru_one *
> list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
> {
> - /*
> - * The lock protects the array of per cgroup lists from relocation
> - * (see memcg_update_list_lru_node).
> - */
> - lockdep_assert_held(&nlru->lock);
> - if (nlru->memcg_lrus && idx >= 0)
> - return nlru->memcg_lrus->lru[idx];
> + struct list_lru_memcg *tmp;
> +
> + WARN_ON_ONCE(!rcu_read_lock_held());
> +
> + tmp = rcu_dereference(nlru->memcg_lrus);
> + if (tmp && idx >= 0)
> + return rcu_dereference(tmp->lru[idx]);
>
> return &nlru->lru;
> }
> @@ -113,14 +113,17 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
> struct list_lru_one *l;
>
> spin_lock(&nlru->lock);
> + rcu_read_lock();
> if (list_empty(item)) {
> l = list_lru_from_kmem(nlru, item);
> list_add_tail(item, &l->list);
> l->nr_items++;
> nlru->nr_items++;
> + rcu_read_unlock();
> spin_unlock(&nlru->lock);
> return true;
> }
> + rcu_read_unlock();
> spin_unlock(&nlru->lock);
> return false;
> }
> @@ -133,14 +136,17 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
> struct list_lru_one *l;
>
> spin_lock(&nlru->lock);
> + rcu_read_lock();
> if (!list_empty(item)) {
> l = list_lru_from_kmem(nlru, item);
> list_del_init(item);
> l->nr_items--;
> nlru->nr_items--;
> + rcu_read_unlock();
> spin_unlock(&nlru->lock);
> return true;
> }
> + rcu_read_unlock();
> spin_unlock(&nlru->lock);
> return false;
> }
> @@ -166,12 +172,13 @@ static unsigned long __list_lru_count_one(struct list_lru *lru,
> {
> struct list_lru_node *nlru = &lru->node[nid];
> struct list_lru_one *l;
> - unsigned long count;
> + unsigned long count = 0;
>
> - spin_lock(&nlru->lock);
> + rcu_read_lock();
> l = list_lru_from_memcg_idx(nlru, memcg_idx);
> - count = l->nr_items;
> - spin_unlock(&nlru->lock);
> + if (l)
> + count = l->nr_items;
> + rcu_read_unlock();
>
> return count;
> }
> @@ -204,6 +211,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
> unsigned long isolated = 0;
>
> spin_lock(&nlru->lock);
> + rcu_read_lock();
> l = list_lru_from_memcg_idx(nlru, memcg_idx);
> restart:
> list_for_each_safe(item, n, &l->list) {
> @@ -250,6 +258,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
> }
> }
>
> + rcu_read_unlock();
> spin_unlock(&nlru->lock);
> return isolated;
> }
> @@ -296,9 +305,14 @@ static void __memcg_destroy_list_lru_node(struct list_lru_memcg *memcg_lrus,
> int begin, int end)
> {
> int i;
> + struct list_lru_one *tmp;
>
> - for (i = begin; i < end; i++)
> - kfree(memcg_lrus->lru[i]);
> + for (i = begin; i < end; i++) {
> + tmp = memcg_lrus->lru[i];
> + rcu_assign_pointer(memcg_lrus->lru[i], NULL);
> + if (tmp)
> + kfree_rcu(tmp, rcu);
> + }
> }
>
> static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> @@ -314,7 +328,7 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> goto fail;
>
> init_one_lru(l);
> - memcg_lrus->lru[i] = l;
> + rcu_assign_pointer(memcg_lrus->lru[i], l);
> }
> return 0;
> fail:
> @@ -325,25 +339,37 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> static int memcg_init_list_lru_node(struct list_lru_node *nlru)
> {
> int size = memcg_nr_cache_ids;
> + struct list_lru_memcg *tmp;
>
> - nlru->memcg_lrus = kvmalloc(size * sizeof(void *), GFP_KERNEL);
> - if (!nlru->memcg_lrus)
> + tmp = kvmalloc(size * sizeof(void *), GFP_KERNEL);
> + if (!tmp)
> return -ENOMEM;
>
> - if (__memcg_init_list_lru_node(nlru->memcg_lrus, 0, size)) {
> - kvfree(nlru->memcg_lrus);
> + if (__memcg_init_list_lru_node(tmp, 0, size)) {
> + kvfree(tmp);
> return -ENOMEM;
> }
>
> + rcu_assign_pointer(nlru->memcg_lrus, tmp);
> +
> return 0;
> }
>
> -static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
> +static void memcg_destroy_list_lru_node_rcu(struct rcu_head *rcu)
> {
> + struct list_lru_node *nlru;
> +
> + nlru = container_of(rcu, struct list_lru_node, rcu);
> +
> __memcg_destroy_list_lru_node(nlru->memcg_lrus, 0, memcg_nr_cache_ids);
> kvfree(nlru->memcg_lrus);
> }
>
> +static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
> +{
> + call_rcu(&nlru->rcu, memcg_destroy_list_lru_node_rcu);
> +}
> +
> static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> int old_size, int new_size)
> {
> @@ -371,9 +397,10 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> * we have to use IRQ-safe primitives here to avoid deadlock.
> */
> spin_lock_irq(&nlru->lock);
> - nlru->memcg_lrus = new;
> + rcu_assign_pointer(nlru->memcg_lrus, new);
> spin_unlock_irq(&nlru->lock);
>
> + synchronize_rcu();
> kvfree(old);
> return 0;
> }
> @@ -487,6 +514,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
> * we have to use IRQ-safe primitives here to avoid deadlock.
> */
> spin_lock_irq(&nlru->lock);
> + rcu_read_lock();
>
> src = list_lru_from_memcg_idx(nlru, src_idx);
> dst = list_lru_from_memcg_idx(nlru, dst_idx);
> @@ -495,6 +523,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
> dst->nr_items += src->nr_items;
> src->nr_items = 0;
>
> + rcu_read_unlock();
> spin_unlock_irq(&nlru->lock);
> }
>
> --
> 2.11.0
--
Michal Hocko
SUSE Labs
[Cc Kirill]
AFAIU this has already been fixed in exactly the same fashion by Kirill
(mmotm commit 8e7d1201ec71 "mm: make counting of list_lru_one::nr_items
lockless"). Kirill is working on further optimizations right now, see
https://lkml.kernel.org/r/152163840790.21546.980703278415599202.stgit@localhost.localdomain
On Tue, Mar 27, 2018 at 10:15:46AM +0200, Michal Hocko wrote:
> [CC Dave]
>
> On Tue 27-03-18 15:59:04, Li RongQing wrote:
> > when reclaim memory, shink_slab will take lots of time even if
> > no memory is reclaimed, since list_lru_count_one called by it
> > needs to take a spinlock
> >
> > try to optimize it by replacing spinlock with RCU in
> > __list_lru_count_one
>
> Isn't the RCU overkill here? Why cannot we simply do an optimistic
> lockless check for nr_items? It would be racy but does it actually
> matter? We should be able to tolerate occasional 0 to non-zero and vice
> versa transitions AFAICS.
>
> >
> > $dd if=aaa of=bbb bs=1k count=3886080
> > $rm -f bbb
> > $time echo 100000000 >/cgroup/memory/test/memory.limit_in_bytes
> >
> > Before: 0m0.415s ===> after: 0m0.395s
> >
> > Signed-off-by: Li RongQing <[email protected]>
> > ---
> > include/linux/list_lru.h | 2 ++
> > mm/list_lru.c | 69 ++++++++++++++++++++++++++++++++++--------------
> > 2 files changed, 51 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> > index bb8129a3474d..ae472538038e 100644
> > --- a/include/linux/list_lru.h
> > +++ b/include/linux/list_lru.h
> > @@ -29,6 +29,7 @@ struct list_lru_one {
> > struct list_head list;
> > /* may become negative during memcg reparenting */
> > long nr_items;
> > + struct rcu_head rcu;
> > };
> >
> > struct list_lru_memcg {
> > @@ -46,6 +47,7 @@ struct list_lru_node {
> > struct list_lru_memcg *memcg_lrus;
> > #endif
> > long nr_items;
> > + struct rcu_head rcu;
> > } ____cacheline_aligned_in_smp;
> >
> > struct list_lru {
> > diff --git a/mm/list_lru.c b/mm/list_lru.c
> > index fd41e969ede5..4c58ed861729 100644
> > --- a/mm/list_lru.c
> > +++ b/mm/list_lru.c
> > @@ -52,13 +52,13 @@ static inline bool list_lru_memcg_aware(struct list_lru *lru)
> > static inline struct list_lru_one *
> > list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
> > {
> > - /*
> > - * The lock protects the array of per cgroup lists from relocation
> > - * (see memcg_update_list_lru_node).
> > - */
> > - lockdep_assert_held(&nlru->lock);
> > - if (nlru->memcg_lrus && idx >= 0)
> > - return nlru->memcg_lrus->lru[idx];
> > + struct list_lru_memcg *tmp;
> > +
> > + WARN_ON_ONCE(!rcu_read_lock_held());
> > +
> > + tmp = rcu_dereference(nlru->memcg_lrus);
> > + if (tmp && idx >= 0)
> > + return rcu_dereference(tmp->lru[idx]);
> >
> > return &nlru->lru;
> > }
> > @@ -113,14 +113,17 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
> > struct list_lru_one *l;
> >
> > spin_lock(&nlru->lock);
> > + rcu_read_lock();
> > if (list_empty(item)) {
> > l = list_lru_from_kmem(nlru, item);
> > list_add_tail(item, &l->list);
> > l->nr_items++;
> > nlru->nr_items++;
> > + rcu_read_unlock();
> > spin_unlock(&nlru->lock);
> > return true;
> > }
> > + rcu_read_unlock();
> > spin_unlock(&nlru->lock);
> > return false;
> > }
> > @@ -133,14 +136,17 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item)
> > struct list_lru_one *l;
> >
> > spin_lock(&nlru->lock);
> > + rcu_read_lock();
> > if (!list_empty(item)) {
> > l = list_lru_from_kmem(nlru, item);
> > list_del_init(item);
> > l->nr_items--;
> > nlru->nr_items--;
> > + rcu_read_unlock();
> > spin_unlock(&nlru->lock);
> > return true;
> > }
> > + rcu_read_unlock();
> > spin_unlock(&nlru->lock);
> > return false;
> > }
> > @@ -166,12 +172,13 @@ static unsigned long __list_lru_count_one(struct list_lru *lru,
> > {
> > struct list_lru_node *nlru = &lru->node[nid];
> > struct list_lru_one *l;
> > - unsigned long count;
> > + unsigned long count = 0;
> >
> > - spin_lock(&nlru->lock);
> > + rcu_read_lock();
> > l = list_lru_from_memcg_idx(nlru, memcg_idx);
> > - count = l->nr_items;
> > - spin_unlock(&nlru->lock);
> > + if (l)
> > + count = l->nr_items;
> > + rcu_read_unlock();
> >
> > return count;
> > }
> > @@ -204,6 +211,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
> > unsigned long isolated = 0;
> >
> > spin_lock(&nlru->lock);
> > + rcu_read_lock();
> > l = list_lru_from_memcg_idx(nlru, memcg_idx);
> > restart:
> > list_for_each_safe(item, n, &l->list) {
> > @@ -250,6 +258,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
> > }
> > }
> >
> > + rcu_read_unlock();
> > spin_unlock(&nlru->lock);
> > return isolated;
> > }
> > @@ -296,9 +305,14 @@ static void __memcg_destroy_list_lru_node(struct list_lru_memcg *memcg_lrus,
> > int begin, int end)
> > {
> > int i;
> > + struct list_lru_one *tmp;
> >
> > - for (i = begin; i < end; i++)
> > - kfree(memcg_lrus->lru[i]);
> > + for (i = begin; i < end; i++) {
> > + tmp = memcg_lrus->lru[i];
> > + rcu_assign_pointer(memcg_lrus->lru[i], NULL);
> > + if (tmp)
> > + kfree_rcu(tmp, rcu);
> > + }
> > }
> >
> > static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> > @@ -314,7 +328,7 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> > goto fail;
> >
> > init_one_lru(l);
> > - memcg_lrus->lru[i] = l;
> > + rcu_assign_pointer(memcg_lrus->lru[i], l);
> > }
> > return 0;
> > fail:
> > @@ -325,25 +339,37 @@ static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
> > static int memcg_init_list_lru_node(struct list_lru_node *nlru)
> > {
> > int size = memcg_nr_cache_ids;
> > + struct list_lru_memcg *tmp;
> >
> > - nlru->memcg_lrus = kvmalloc(size * sizeof(void *), GFP_KERNEL);
> > - if (!nlru->memcg_lrus)
> > + tmp = kvmalloc(size * sizeof(void *), GFP_KERNEL);
> > + if (!tmp)
> > return -ENOMEM;
> >
> > - if (__memcg_init_list_lru_node(nlru->memcg_lrus, 0, size)) {
> > - kvfree(nlru->memcg_lrus);
> > + if (__memcg_init_list_lru_node(tmp, 0, size)) {
> > + kvfree(tmp);
> > return -ENOMEM;
> > }
> >
> > + rcu_assign_pointer(nlru->memcg_lrus, tmp);
> > +
> > return 0;
> > }
> >
> > -static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
> > +static void memcg_destroy_list_lru_node_rcu(struct rcu_head *rcu)
> > {
> > + struct list_lru_node *nlru;
> > +
> > + nlru = container_of(rcu, struct list_lru_node, rcu);
> > +
> > __memcg_destroy_list_lru_node(nlru->memcg_lrus, 0, memcg_nr_cache_ids);
> > kvfree(nlru->memcg_lrus);
> > }
> >
> > +static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
> > +{
> > + call_rcu(&nlru->rcu, memcg_destroy_list_lru_node_rcu);
> > +}
> > +
> > static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> > int old_size, int new_size)
> > {
> > @@ -371,9 +397,10 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
> > * we have to use IRQ-safe primitives here to avoid deadlock.
> > */
> > spin_lock_irq(&nlru->lock);
> > - nlru->memcg_lrus = new;
> > + rcu_assign_pointer(nlru->memcg_lrus, new);
> > spin_unlock_irq(&nlru->lock);
> >
> > + synchronize_rcu();
> > kvfree(old);
> > return 0;
> > }
> > @@ -487,6 +514,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
> > * we have to use IRQ-safe primitives here to avoid deadlock.
> > */
> > spin_lock_irq(&nlru->lock);
> > + rcu_read_lock();
> >
> > src = list_lru_from_memcg_idx(nlru, src_idx);
> > dst = list_lru_from_memcg_idx(nlru, dst_idx);
> > @@ -495,6 +523,7 @@ static void memcg_drain_list_lru_node(struct list_lru_node *nlru,
> > dst->nr_items += src->nr_items;
> > src->nr_items = 0;
> >
> > + rcu_read_unlock();
> > spin_unlock_irq(&nlru->lock);
> > }
> >
> > --
> > 2.11.0
>
> --
> Michal Hocko
> SUSE Labs
>
Hi Li,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on linus/master]
[also build test WARNING on v4.16-rc7]
[cannot apply to next-20180327]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Li-RongQing/mm-list_lru-replace-spinlock-with-RCU-in-__list_lru_count_one/20180328-042620
reproduce:
# apt-get install sparse
make ARCH=x86_64 allmodconfig
make C=1 CF=-D__CHECK_ENDIAN__
sparse warnings: (new ones prefixed by >>)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
>> mm/list_lru.c:59:15: sparse: incompatible types in comparison expression (different address spaces)
mm/list_lru.c:61:24: sparse: incompatible types in comparison expression (different address spaces)
vim +59 mm/list_lru.c
51
52 static inline struct list_lru_one *
53 list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
54 {
55 struct list_lru_memcg *tmp;
56
57 WARN_ON_ONCE(!rcu_read_lock_held());
58
> 59 tmp = rcu_dereference(nlru->memcg_lrus);
60 if (tmp && idx >= 0)
61 return rcu_dereference(tmp->lru[idx]);
62
63 return &nlru->lru;
64 }
65
---
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