[PATCH net-next 0/2] net: fix memcg overhead caused by sk->sk_forward_alloc size

[Cathy Zhang <cathy.zhang@intel.com>]

Dear Reviewers,

memcg charge overhead is observed while we benchmark memcached with
memtier by running containers. It's caused by commit 4890b686f408 ("net:
Keep sk->sk_forward_alloc as small as possible"), which aims to reduce
system memory pressure, but makes the per-socket forward allocated
memory too small. The impact of this change is to trigger more
frequently memory allocation during TCP connection lifecycle and leads
to memcg charge overhead finally.

To avoid memcg charge overhead mentioned above, this series defines 64KB
as reclaim threshold when uncharging per-socket memory. It reduces the
frequency of memory allocation and charging during TCP connection, and
it's much less than the original 2MB per-socket reserved memory before
commit 4890b686f408 ("net: keep sk->sk_forward_alloc as small as
possibile"). Run memcached/memtier test with the 64KB reclaim threshold,
RPS gains around 2.07x.

This series also provides a new ABI /proc/sys/net/core/reclaim_threshold
with flexibility to tune the reclaim threshold according to system
running status.

This series is based on the latest net-next/main tree.

Thanks for your time to help review and your feedback will be greatly!

Cathy Zhang (2):
  net: Keep sk->sk_forward_alloc as a proper size
  net: Add sysctl_reclaim_threshold

 Documentation/admin-guide/sysctl/net.rst | 12 +++++++++
 include/net/sock.h                       | 32 +++++++++++++++++++++++-
 net/core/sysctl_net_core.c               | 14 +++++++++++
 3 files changed, 57 insertions(+), 1 deletion(-)


base-commit: ed23734c23d2fc1e6a1ff80f8c2b82faeed0ed0c
2.34.1