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Date: Thu, 5 Mar 2020 13:17:09 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: Shakeel Butt <shakeelb@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Roman Gushchin <guro@...com> Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, "David S . Miller" <davem@...emloft.net>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, netdev@...r.kernel.org, linux-mm@...ck.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3] net: memcg: late association of sock to memcg On 3/5/20 12:55 PM, Shakeel Butt wrote: > If a TCP socket is allocated in IRQ context or cloned from unassociated > (i.e. not associated to a memcg) in IRQ context then it will remain > unassociated for its whole life. Almost half of the TCPs created on the > system are created in IRQ context, so, memory used by such sockets will > not be accounted by the memcg. > > This issue is more widespread in cgroup v1 where network memory > accounting is opt-in but it can happen in cgroup v2 if the source socket > for the cloning was created in root memcg. > > To fix the issue, just do the late association of the unassociated > sockets at accept() time in the process context and then force charge > the memory buffer already reserved by the socket. > > Signed-off-by: Shakeel Butt <shakeelb@...gle.com> > --- > Changes since v2: > - Additional check for charging. > - Release the sock after charging. > > Changes since v1: > - added sk->sk_rmem_alloc to initial charging. > - added synchronization to get memory usage and set sk_memcg race-free. > > net/ipv4/inet_connection_sock.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c > index a4db79b1b643..5face55cf818 100644 > --- a/net/ipv4/inet_connection_sock.c > +++ b/net/ipv4/inet_connection_sock.c > @@ -482,6 +482,26 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern) > } > spin_unlock_bh(&queue->fastopenq.lock); > } > + > + if (mem_cgroup_sockets_enabled && !newsk->sk_memcg) { > + int amt; > + > + /* atomically get the memory usage, set and charge the > + * sk->sk_memcg. > + */ > + lock_sock(newsk); > + > + /* The sk has not been accepted yet, no need to look at > + * sk->sk_wmem_queued. > + */ > + amt = sk_mem_pages(newsk->sk_forward_alloc + > + atomic_read(&sk->sk_rmem_alloc)); > + mem_cgroup_sk_alloc(newsk); > + if (newsk->sk_memcg && amt) > + mem_cgroup_charge_skmem(newsk->sk_memcg, amt); > + > + release_sock(newsk); > + } > out: > release_sock(sk); > if (req) > This patch looks fine, but why keeping the mem_cgroup_sk_alloc(newsk); in sk_clone_lock() ? Note that all TCP sk_clone_lock() calls happen in softirq context.
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