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: <CAAVpQUAAVF==Db=1xj7bbrbiu-tPNxt3Y43CPhy6=X7-+huc7A@mail.gmail.com>
Date: Tue, 2 Sep 2025 13:45:59 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Shakeel Butt <shakeel.butt@...ux.dev>, 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 Tue, Sep 2, 2025 at 1:17 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> 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) ?

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?
>
> >               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;
> >               }
>