Re: [PATCH net-next 6/7] net: keep sk->sk_forward_alloc as small as possible

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Wed, 8 Jun 2022, Eric Dumazet wrote:

> From: Eric Dumazet <edumazet@google.com>
>
> Currently, tcp_memory_allocated can hit tcp_mem[] limits quite fast.
>
> Each TCP socket can forward allocate up to 2 MB of memory, even after
> flow became less active.
>
> 10,000 sockets can have reserved 20 GB of memory,
> and we have no shrinker in place to reclaim that.
>
> Instead of trying to reclaim the extra allocations in some places,
> just keep sk->sk_forward_alloc values as small as possible.
>
> This should not impact performance too much now we have per-cpu
> reserves: Changes to tcp_memory_allocated should not be too frequent.
>
> For sockets not using SO_RESERVE_MEM:
> - idle sockets (no packets in tx/rx queues) have zero forward alloc.
> - non idle sockets have a forward alloc smaller than one page.
>
> Note:
>
> - Removal of SK_RECLAIM_CHUNK and SK_RECLAIM_THRESHOLD
>   is left to MPTCP maintainers as a follow up.

Yes, noted. Will be sure to clean this up.

Thanks Eric.


>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
> include/net/sock.h           | 29 ++---------------------------
> net/core/datagram.c          |  3 ---
> net/ipv4/tcp.c               |  7 -------
> net/ipv4/tcp_input.c         |  4 ----
> net/ipv4/tcp_timer.c         | 19 ++++---------------
> net/iucv/af_iucv.c           |  2 --
> net/mptcp/protocol.c         |  2 +-
> net/sctp/sm_statefuns.c      |  2 --
> net/sctp/socket.c            |  5 -----
> net/sctp/stream_interleave.c |  2 --
> net/sctp/ulpqueue.c          |  4 ----
> 11 files changed, 7 insertions(+), 72 deletions(-)
>

--
Mat Martineau
Intel