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Message-ID: <20250314061511.1308152-11-shakeel.butt@linux.dev>
Date: Thu, 13 Mar 2025 23:15:11 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>,
Vlastimil Babka <vbabka@...e.cz>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
linux-mm@...ck.org,
cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
Meta kernel team <kernel-team@...a.com>
Subject: [RFC PATCH 10/10] memcg: no more irq disabling for stock locks
Let's switch all memcg_stock locks acquire and release places to not
disable and enable irqs. There are two still functions (i.e.
mod_objcg_state() and drain_obj_stock) which needs to disable irqs to
update the stats on non-RT kernels. For now add a simple wrapper for
that functionality.
Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
mm/memcontrol.c | 83 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 54 insertions(+), 29 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ba5d004049d3..fa28efa298f4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1796,22 +1796,17 @@ 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,
- gfp_t gfp_mask)
+static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
struct memcg_stock_pcp *stock;
unsigned int stock_pages;
- unsigned long flags;
bool ret = false;
if (nr_pages > MEMCG_CHARGE_BATCH)
return ret;
- if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
- if (!gfpflags_allow_spinning(gfp_mask))
+ if (!localtry_trylock(&memcg_stock.stock_lock))
return ret;
- localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
- }
stock = this_cpu_ptr(&memcg_stock);
stock_pages = READ_ONCE(stock->nr_pages);
@@ -1820,7 +1815,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages,
ret = true;
}
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
return ret;
}
@@ -1855,7 +1850,6 @@ static void drain_stock(struct memcg_stock_pcp *stock)
static void drain_local_stock(struct work_struct *dummy)
{
struct memcg_stock_pcp *stock;
- unsigned long flags;
lockdep_assert_once(in_task());
@@ -1864,14 +1858,14 @@ 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
*/
- localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
+ localtry_lock(&memcg_stock.stock_lock);
stock = this_cpu_ptr(&memcg_stock);
drain_obj_stock(stock);
drain_stock(stock);
clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
}
/* Should never be called with root_mem_cgroup. */
@@ -1879,9 +1873,8 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
struct memcg_stock_pcp *stock;
unsigned int stock_pages;
- unsigned long flags;
- if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
+ if (!localtry_trylock(&memcg_stock.stock_lock)) {
/*
* In case of unlikely failure to lock percpu stock_lock
* uncharge memcg directly.
@@ -1902,7 +1895,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
if (stock_pages > MEMCG_CHARGE_BATCH)
drain_stock(stock);
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
}
/*
@@ -1953,17 +1946,12 @@ void drain_all_stock(struct mem_cgroup *root_memcg)
static int memcg_hotplug_cpu_dead(unsigned int cpu)
{
struct memcg_stock_pcp *stock;
- unsigned long flags;
lockdep_assert_once(in_task());
stock = &per_cpu(memcg_stock, cpu);
- /* drain_obj_stock requires stock_lock */
- localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
drain_obj_stock(stock);
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
-
drain_stock(stock);
return 0;
@@ -2254,7 +2242,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
unsigned long pflags;
retry:
- if (consume_stock(memcg, nr_pages, gfp_mask))
+ if (consume_stock(memcg, nr_pages))
return 0;
if (!gfpflags_allow_spinning(gfp_mask))
@@ -2757,6 +2745,28 @@ static void replace_stock_objcg(struct memcg_stock_pcp *stock,
WRITE_ONCE(stock->cached_objcg, objcg);
}
+static unsigned long rt_lock(void)
+{
+#ifdef CONFIG_PREEMPT_RT
+ migrate_disable();
+ return 0;
+#else
+ unsigned long flags = 0;
+
+ local_irq_save(flags);
+ return flags;
+#endif
+}
+
+static void rt_unlock(unsigned long flags)
+{
+#ifdef CONFIG_PREEMPT_RT
+ migrate_enable();
+#else
+ local_irq_restore(flags);
+#endif
+}
+
static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
enum node_stat_item idx, int nr)
{
@@ -2764,7 +2774,8 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
unsigned long flags;
int *bytes;
- if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
+ if (!localtry_trylock(&memcg_stock.stock_lock)) {
+ /* Do we need mix_rt_[un]lock here too. */
__mod_objcg_mlstate(objcg, pgdat, idx, nr);
return;
}
@@ -2783,6 +2794,8 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
/* Flush the existing cached vmstat data */
struct pglist_data *oldpg = stock->cached_pgdat;
+ flags = rt_lock();
+
if (stock->nr_slab_reclaimable_b) {
__mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B,
stock->nr_slab_reclaimable_b);
@@ -2793,6 +2806,8 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
stock->nr_slab_unreclaimable_b);
stock->nr_slab_unreclaimable_b = 0;
}
+
+ rt_unlock(flags);
stock->cached_pgdat = pgdat;
}
@@ -2814,19 +2829,21 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
nr = 0;
}
}
- if (nr)
+ if (nr) {
+ flags = rt_lock();
__mod_objcg_mlstate(objcg, pgdat, idx, nr);
+ rt_unlock(flags);
+ }
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
}
static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
{
struct memcg_stock_pcp *stock;
- unsigned long flags;
bool ret = false;
- if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags))
+ if (!localtry_trylock(&memcg_stock.stock_lock))
return ret;
stock = this_cpu_ptr(&memcg_stock);
@@ -2835,7 +2852,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
ret = true;
}
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
return ret;
}
@@ -2843,10 +2860,16 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
static void drain_obj_stock(struct memcg_stock_pcp *stock)
{
struct obj_cgroup *old = READ_ONCE(stock->cached_objcg);
+ unsigned long flags;
+ bool locked = stock->nr_bytes || stock->nr_slab_reclaimable_b ||
+ stock->nr_slab_unreclaimable_b;
if (!old)
return;
+ if (locked)
+ flags = rt_lock();
+
if (stock->nr_bytes) {
unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT;
unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);
@@ -2897,6 +2920,9 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
stock->cached_pgdat = NULL;
}
+ if (locked)
+ rt_unlock(flags);
+
WRITE_ONCE(stock->cached_objcg, NULL);
obj_cgroup_put(old);
}
@@ -2920,10 +2946,9 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
bool allow_uncharge)
{
struct memcg_stock_pcp *stock;
- unsigned long flags;
unsigned int nr_pages = 0;
- if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
+ if (!localtry_trylock(&memcg_stock.stock_lock)) {
atomic_add(nr_bytes, &objcg->nr_charged_bytes);
return;
}
@@ -2940,7 +2965,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
stock->nr_bytes &= (PAGE_SIZE - 1);
}
- localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags);
+ localtry_unlock(&memcg_stock.stock_lock);
if (nr_pages)
obj_cgroup_uncharge_pages(objcg, nr_pages);
--
2.47.1
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