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Subject[PATCH net-next] net, mm: avoid unnecessary memcg charge skmem
Date
In __sk_mem_raise_allocated(), if mem_cgroup_charge_skmem() return
false, mem_cgroup_uncharge_skmem will be executed.

The logic is as bellow,
__sk_mem_raise_allocated
ret = mem_cgroup_uncharge_skmem
try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
return false
if (!ret)
mem_cgroup_uncharge_skmem(sk->sk_memcg, amt);

So it is unnecessary to charge if it is not forced.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/memcontrol.h | 3 ++-
mm/memcontrol.c | 12 +++++++++---
net/core/sock.c | 5 +++--
net/ipv4/tcp_output.c | 2 +-
4 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6c6fb11..56c07c9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1160,7 +1160,8 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,
#endif /* CONFIG_CGROUP_WRITEBACK */

struct sock;
-bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
+bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
+ bool force);
void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
#ifdef CONFIG_MEMCG
extern struct static_key_false memcg_sockets_enabled_key;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e6f0d5e..1122be2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5929,7 +5929,8 @@ void mem_cgroup_sk_free(struct sock *sk)
* Charges @nr_pages to @memcg. Returns %true if the charge fit within
* @memcg's configured limit, %false if the charge had to be forced.
*/
-bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
+bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
+ bool force)
{
gfp_t gfp_mask = GFP_KERNEL;

@@ -5940,7 +5941,10 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
memcg->tcpmem_pressure = 0;
return true;
}
- page_counter_charge(&memcg->tcpmem, nr_pages);
+
+ if (force)
+ page_counter_charge(&memcg->tcpmem, nr_pages);
+
memcg->tcpmem_pressure = 1;
return false;
}
@@ -5954,7 +5958,9 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
if (try_charge(memcg, gfp_mask, nr_pages) == 0)
return true;

- try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
+ if (force)
+ try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
+
return false;
}

diff --git a/net/core/sock.c b/net/core/sock.c
index bcc4182..148a840 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2401,9 +2401,10 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
{
struct proto *prot = sk->sk_prot;
long allocated = sk_memory_allocated_add(sk, amt);
+ bool charged = false;

if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
- !mem_cgroup_charge_skmem(sk->sk_memcg, amt))
+ !(charged = mem_cgroup_charge_skmem(sk->sk_memcg, amt, false)))
goto suppress_allocation;

/* Under limit. */
@@ -2465,7 +2466,7 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)

sk_memory_allocated_sub(sk, amt);

- if (mem_cgroup_sockets_enabled && sk->sk_memcg)
+ if (mem_cgroup_sockets_enabled && sk->sk_memcg && charged)
mem_cgroup_uncharge_skmem(sk->sk_memcg, amt);

return 0;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f8f6129..9b741d4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3014,7 +3014,7 @@ void sk_forced_mem_schedule(struct sock *sk, int size)
sk_memory_allocated_add(sk, amt);

if (mem_cgroup_sockets_enabled && sk->sk_memcg)
- mem_cgroup_charge_skmem(sk->sk_memcg, amt);
+ mem_cgroup_charge_skmem(sk->sk_memcg, amt, true);
}

/* Send a FIN. The caller locks the socket for us.
--
1.8.3.1
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