For now __sk_mem_raise_allocated() mainly considers global socket
memory pressure and allows to raise if no global pressure observed,
including the sockets whose memcgs are in pressure, which might
result in longer memcg memstall.

So take net-memcg's pressure into consideration when allocating
socket memory to alleviate long tail latencies.

Signed-off-by: Abel Wu <redacted>
---
 net/core/sock.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 801df091e37a..b899e0b9feda 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c

@@ -2976,22 +2976,31 @@ EXPORT_SYMBOL(sk_wait_data);
 int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
 {
 	bool memcg_charge = mem_cgroup_sockets_enabled && sk->sk_memcg;
+	bool charged = true, pressured = false;
 	struct proto *prot = sk->sk_prot;
-	bool charged = true;
 	long allocated;
 
 	sk_memory_allocated_add(sk, amt);
 	allocated = sk_memory_allocated(sk);
-	if (memcg_charge &&
-	    !(charged = mem_cgroup_charge_skmem(sk->sk_memcg, amt,
-						gfp_memcg_charge())))
-		goto suppress_allocation;
+
+	if (memcg_charge) {
+		charged = mem_cgroup_charge_skmem(sk->sk_memcg, amt,
+						  gfp_memcg_charge());
+		if (!charged)
+			goto suppress_allocation;
+		if (mem_cgroup_under_socket_pressure(sk->sk_memcg))
+			pressured = true;
+	}
 
 	/* Under limit. */
-	if (allocated <= sk_prot_mem_limits(sk, 0)) {
+	if (allocated <= sk_prot_mem_limits(sk, 0))
 		sk_leave_memory_pressure(sk);
+	else
+		pressured = true;