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Message-ID: <CACSApvamXCUBJ_aCumkj5abTwnBCpHij2Gwx514-NyMNqt7Khw@mail.gmail.com>
Date: Thu, 9 Jun 2022 09:33:53 -0400
From: Soheil Hassas Yeganeh <soheil@...gle.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
netdev <netdev@...r.kernel.org>, Wei Wang <weiwan@...gle.com>,
Shakeel Butt <shakeelb@...gle.com>,
Neal Cardwell <ncardwell@...gle.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 0/7] net: reduce tcp_memory_allocated inflation
On Thu, Jun 9, 2022 at 2:34 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
>
> Hosts with a lot of sockets tend to hit so called TCP memory pressure,
> leading to very bad TCP performance and/or OOM.
>
> The problem is that some TCP sockets can hold up to 2MB of 'forward
> allocations' in their per-socket cache (sk->sk_forward_alloc),
> and there is no mechanism to make them relinquish their share
> under mem pressure.
> Only under some potentially rare events their share is reclaimed,
> one socket at a time.
>
> In this series, I implemented a per-cpu cache instead of a per-socket one.
>
> Each CPU has a +1/-1 MB (256 pages on x86) forward alloc cache, in order
> to not dirty tcp_memory_allocated shared cache line too often.
>
> We keep sk->sk_forward_alloc values as small as possible, to meet
> memcg page granularity constraint.
>
> Note that memcg already has a per-cpu cache, although MEMCG_CHARGE_BATCH
> is defined to 32 pages, which seems a bit small.
>
> Note that while this cover letter mentions TCP, this work is generic
> and supports TCP, UDP, DECNET, SCTP.
>
> Eric Dumazet (7):
> Revert "net: set SK_MEM_QUANTUM to 4096"
> net: remove SK_MEM_QUANTUM and SK_MEM_QUANTUM_SHIFT
> net: add per_cpu_fw_alloc field to struct proto
> net: implement per-cpu reserves for memory_allocated
> net: fix sk_wmem_schedule() and sk_rmem_schedule() errors
> net: keep sk->sk_forward_alloc as small as possible
> net: unexport __sk_mem_{raise|reduce}_allocated
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Very nice work! Thank you for scaling up TCP again!
> include/net/sock.h | 100 +++++++++++++++--------------------
> include/net/tcp.h | 2 +
> include/net/udp.h | 1 +
> net/core/datagram.c | 3 --
> net/core/sock.c | 22 ++++----
> net/decnet/af_decnet.c | 4 ++
> net/ipv4/tcp.c | 13 ++---
> net/ipv4/tcp_input.c | 6 +--
> net/ipv4/tcp_ipv4.c | 3 ++
> net/ipv4/tcp_output.c | 2 +-
> net/ipv4/tcp_timer.c | 19 ++-----
> net/ipv4/udp.c | 14 +++--
> net/ipv4/udplite.c | 3 ++
> net/ipv6/tcp_ipv6.c | 3 ++
> net/ipv6/udp.c | 3 ++
> net/ipv6/udplite.c | 3 ++
> net/iucv/af_iucv.c | 2 -
> net/mptcp/protocol.c | 13 +++--
> net/sctp/protocol.c | 4 +-
> net/sctp/sm_statefuns.c | 2 -
> net/sctp/socket.c | 12 +++--
> net/sctp/stream_interleave.c | 2 -
> net/sctp/ulpqueue.c | 4 --
> 23 files changed, 114 insertions(+), 126 deletions(-)
>
> --
> 2.36.1.255.ge46751e96f-goog
>
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