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memcg: Use trylock to access memcg stock_lock.

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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@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20250222024427.30294-5-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2025-02-21 18:44:25 -08:00
parent 8c57b687e8
commit 01d37228d3
1 changed files with 37 additions and 16 deletions
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53
mm/memcontrol.c
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@ -1739,7 +1739,7 @@ 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;
@ -1754,7 +1754,7 @@ 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);
@ -1766,6 +1766,7 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
* consume_stock: Try to consume stocked charge on this cpu.
* @memcg: memcg to consume from.
* @nr_pages: how many pages to charge.
* @gfp_mask: allocation mask.
*
* The charges will only happen if @memcg matches the current cpu's memcg
* stock, and at least @nr_pages are available in that stock. Failure to
@ -1773,7 +1774,8 @@ 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;
@ -1783,7 +1785,11 @@ 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);
@ -1792,7 +1798,7 @@ 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;
}
@ -1831,14 +1837,14 @@ 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);
}
@ -1868,9 +1874,20 @@ 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);
}
/*
@ -2213,9 +2230,13 @@ 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))
@ -2699,7 +2720,7 @@ 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);
/*
@ -2752,7 +2773,7 @@ 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);
}
@ -2762,7 +2783,7 @@ 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) {
@ -2770,7 +2791,7 @@ 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;
}
@ -2862,7 +2883,7 @@ 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 */
@ -2880,7 +2901,7 @@ 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)