Commit 2e12072c authored by Abel Wu's avatar Abel Wu Committed by Paolo Abeni
Browse files

sock: Doc behaviors for pressure heurisitics 



There are now two accounting infrastructures for skmem, while the
heuristics in __sk_mem_raise_allocated() were actually introduced
before memcg was born.

Add some comments to clarify whether they can be applied to both
infrastructures or not.

Suggested-by: default avatarShakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarAbel Wu <wuyun.abel@bytedance.com>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231019120026.42215-2-wuyun.abel@bytedance.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 2def8ff3

net/core/sock.c

+13 −1
Original line number Diff line number Diff line
@@ -3067,7 +3067,14 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind) 
	if (allocated > sk_prot_mem_limits(sk, 2))

		goto suppress_allocation;



	/* guarantee minimum buffer size under pressure */

	/* Guarantee minimum buffer size under pressure (either global

	 * or memcg) to make sure features described in RFC 7323 (TCP

	 * Extensions for High Performance) work properly.

	 *

	 * This rule does NOT stand when exceeds global or memcg's hard

	 * limit, or else a DoS attack can be taken place by spawning

	 * lots of sockets whose usage are under minimum buffer size.

	 */

	if (kind == SK_MEM_RECV) {

		if (atomic_read(&sk->sk_rmem_alloc) < sk_get_rmem0(sk, prot))

			return 1;
@@ -3088,6 +3095,11 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind) 


		if (!sk_under_memory_pressure(sk))

			return 1;



		/* Try to be fair among all the sockets under global

		 * pressure by allowing the ones that below average

		 * usage to raise.

		 */

		alloc = sk_sockets_allocated_read_positive(sk);

		if (sk_prot_mem_limits(sk, 2) > alloc *

		    sk_mem_pages(sk->sk_wmem_queued +