Re: [PATCH v4 bpf-next/net 4/5] net-memcg: Allow decoupling memcg from global protocol memory accounting.

On Tue, Sep 2, 2025 at 1:17 PM Martin KaFai Lau [off-list ref] wrote:

On 8/28/25 6:00 PM, Kuniyuki Iwashima wrote:

quoted

+static inline bool sk_should_enter_memory_pressure(struct sock *sk)
+{
+     return !mem_cgroup_sk_enabled(sk) || !mem_cgroup_sk_isolated(sk);
+}
+
  static inline long
  proto_memory_allocated(const struct proto *prot)
  {

quoted

@@ -3154,8 +3158,11 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
      if (likely(skb_page_frag_refill(32U, pfrag, sk->sk_allocation)))
              return true;

-     sk_enter_memory_pressure(sk);
+     if (sk_should_enter_memory_pressure(sk))
+             sk_enter_memory_pressure(sk);
+
      sk_stream_moderate_sndbuf(sk);
+
      return false;
  }

quoted

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 71a956fbfc55..dcbd49e2f8af 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c

@@ -908,7 +908,8 @@ struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp,
              }
              __kfree_skb(skb);
      } else {
-             sk->sk_prot->enter_memory_pressure(sk);
+             if (sk_should_enter_memory_pressure(sk))
+                     tcp_enter_memory_pressure(sk);

This change from sk_prot->enter_memory_pressure to tcp_enter_memory_pressure
looks fine. A qq / nit, have you thought about checking
sk_should_enter_memory_pressure inside the tcp_enter_memory_pressure(sk) /
sk_enter_memory_pressure(sk) ?

Yes, I wanted to centralise the check to sk_enter_memory_pressure(),
but it calls tcp_enter_memory_pressure() (or sctp one) and they are also
called directly, so I finally placed the check outside of the functions.

Other changes of patch 4 lgtm.

Shakeel, you have ack-ed patch 1. Will you take a look at patch 3 and patch 4 also?

quoted

              sk_stream_moderate_sndbuf(sk);
      }

quoted

@@ -1016,7 +1017,7 @@ static void mptcp_enter_memory_pressure(struct sock *sk)
      mptcp_for_each_subflow(msk, subflow) {
              struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

-             if (first)
+             if (first && sk_should_enter_memory_pressure(ssk))
                      tcp_enter_memory_pressure(ssk);
              sk_stream_moderate_sndbuf(ssk);

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index f672a62a9a52..6696ef837116 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c

@@ -35,6 +35,7 @@
  #include <linux/netdevice.h>
  #include <net/dst.h>
  #include <net/inet_connection_sock.h>
+#include <net/proto_memory.h>
  #include <net/tcp.h>
  #include <net/tls.h>
  #include <linux/skbuff_ref.h>

@@ -371,7 +372,8 @@ static int tls_do_allocation(struct sock *sk,
      if (!offload_ctx->open_record) {
              if (unlikely(!skb_page_frag_refill(prepend_size, pfrag,
                                                 sk->sk_allocation))) {
-                     READ_ONCE(sk->sk_prot)->enter_memory_pressure(sk);
+                     if (sk_should_enter_memory_pressure(sk))
+                             READ_ONCE(sk->sk_prot)->enter_memory_pressure(sk);
                      sk_stream_moderate_sndbuf(sk);
                      return -ENOMEM;
              }