From: Alexei Starovoitov <ast@xxxxxxxxxx>
Teach memcg to operate under trylock conditions when spinning locks
cannot be used.
localtry_trylock might fail and this would lead to charge cache bypass
if the calling context doesn't allow spinning (gfpflags_allow_spinning).
In those cases charge the memcg counter directly and fail early if
that is not possible. This might cause a pre-mature charge failing
but it will allow an opportunistic charging that is safe from
try_alloc_pages path.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
mm/memcontrol.c | 52 ++++++++++++++++++++++++++++++++++---------------
1 file changed, 36 insertions(+), 16 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7b3503d12aaf..f3af615f727c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1722,7 +1722,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
}
struct memcg_stock_pcp {
- local_lock_t stock_lock;
+ localtry_lock_t stock_lock;
struct mem_cgroup *cached; /* this never be root cgroup */
unsigned int nr_pages;
@@ -1737,7 +1737,7 @@ struct memcg_stock_pcp {
#define FLUSHING_CACHED_CHARGE 0
};
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = {
- .stock_lock = INIT_LOCAL_LOCK(stock_lock),
+ .stock_lock = INIT_LOCALTRY_LOCK(stock_lock),
};
static DEFINE_MUTEX(percpu_charge_mutex);
@@ -1756,7 +1756,8 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
*
* returns true if successful, false otherwise.
*/
-static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
+static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages,
+ gfp_t gfp_mask)
{
struct memcg_stock_pcp *stock;
unsigned int stock_pages;
@@ -1766,7 +1767,11 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
if (nr_pages > MEMCG_CHARGE_BATCH)
return ret;
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
+ if (!gfpflags_allow_spinning(gfp_mask))
+ return ret;
+ localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
+ }
stock = this_cpu_ptr(&memcg_stock);
stock_pages = READ_ONCE(stock->nr_pages);
@@ -1775,7 +1780,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
ret = true;
}
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
return ret;
}
@@ -1814,14 +1819,14 @@ 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
*/
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
old = drain_obj_stock(stock);
drain_stock(stock);
clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
obj_cgroup_put(old);
}
@@ -1851,9 +1856,20 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
unsigned long flags;
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
+ /*
+ * In case of unlikely failure to lock percpu stock_lock
+ * uncharge memcg directly.
+ */
+ if (mem_cgroup_is_root(memcg))
+ return;
+ page_counter_uncharge(&memcg->memory, nr_pages);
+ if (do_memsw_account())
+ page_counter_uncharge(&memcg->memsw, nr_pages);
+ return;
+ }
__refill_stock(memcg, nr_pages);
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
}
/*
@@ -2196,9 +2212,13 @@ int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
unsigned long pflags;
retry:
- if (consume_stock(memcg, nr_pages))
+ if (consume_stock(memcg, nr_pages, gfp_mask))
return 0;
+ if (!gfpflags_allow_spinning(gfp_mask))
+ /* Avoid the refill and flush of the older stock */
+ batch = nr_pages;
+
if (!do_memsw_account() ||
page_counter_try_charge(&memcg->memsw, batch, &counter)) {
if (page_counter_try_charge(&memcg->memory, batch, &counter))
@@ -2709,7 +2729,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
unsigned long flags;
int *bytes;
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
/*
@@ -2762,7 +2782,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
if (nr)
__mod_objcg_mlstate(objcg, pgdat, idx, nr);
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
obj_cgroup_put(old);
}
@@ -2772,7 +2792,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
unsigned long flags;
bool ret = false;
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
if (objcg == READ_ONCE(stock->cached_objcg) && stock->nr_bytes >= nr_bytes) {
@@ -2780,7 +2800,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
ret = true;
}
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
return ret;
}
@@ -2872,7 +2892,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
unsigned long flags;
unsigned int nr_pages = 0;
- local_lock_irqsave(&memcg_stock.stock_lock, flags);
+ localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
stock = this_cpu_ptr(&memcg_stock);
if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */
@@ -2890,7 +2910,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
stock->nr_bytes &= (PAGE_SIZE - 1);
}
- local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
obj_cgroup_put(old);
if (nr_pages)
--
2.43.5
