net: make SK_MEMORY_PCPU_RESERV tunable
authorAdam Li <adamli@os.amperecomputing.com>
Mon, 26 Feb 2024 02:24:52 +0000 (02:24 +0000)
committerDavid S. Miller <davem@davemloft.net>
Wed, 28 Feb 2024 09:23:08 +0000 (09:23 +0000)
commit12a686c2e761f1f1f6e6e2117a9ab9c6de2ac8a7
treeab1e92fc373df83576f38b64ceae75f1e8dcb7d7
parentd4beef418c8be893674d747a791923322f4aab20
net: make SK_MEMORY_PCPU_RESERV tunable

This patch adds /proc/sys/net/core/mem_pcpu_rsv sysctl file,
to make SK_MEMORY_PCPU_RESERV tunable.

Commit 3cd3399dd7a8 ("net: implement per-cpu reserves for
memory_allocated") introduced per-cpu forward alloc cache:

"Implement a per-cpu cache of +1/-1 MB, to reduce number
of changes to sk->sk_prot->memory_allocated, which
would otherwise be cause of false sharing."

sk_prot->memory_allocated points to global atomic variable:
atomic_long_t tcp_memory_allocated ____cacheline_aligned_in_smp;

If increasing the per-cpu cache size from 1MB to e.g. 16MB,
changes to sk->sk_prot->memory_allocated can be further reduced.
Performance may be improved on system with many cores.

Signed-off-by: Adam Li <adamli@os.amperecomputing.com>
Reviewed-by: Christoph Lameter (Ampere) <cl@linux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Documentation/admin-guide/sysctl/net.rst
include/net/sock.h
net/core/sock.c
net/core/sysctl_net_core.c