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

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Message-ID: <4334e29b-1cd0-48ba-9afa-54d01b1b7143@linux.dev>
Date: Tue, 2 Sep 2025 13:16:50 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>,
 Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 John Fastabend <john.fastabend@...il.com>,
 Stanislav Fomichev <sdf@...ichev.me>, Johannes Weiner <hannes@...xchg.org>,
 Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
 Mina Almasry <almasrymina@...gle.com>, Kuniyuki Iwashima
 <kuni1840@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v4 bpf-next/net 4/5] net-memcg: Allow decoupling memcg
 from global protocol memory accounting.

On 8/28/25 6:00 PM, Kuniyuki Iwashima wrote:
> +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)
>   {

> @@ -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;
>   }

> 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) ?

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?

>   		sk_stream_moderate_sndbuf(sk);
>   	}

> @@ -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;
>   		}