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sock: Doc behaviors for pressure heurisitics

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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: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231019120026.42215-2-wuyun.abel@bytedance.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Abel Wu 2023-10-19 20:00:25 +08:00 committed by Paolo Abeni
parent 2def8ff3fd
commit 2e12072c67
1 changed files with 13 additions and 1 deletions
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14
net/core/sock.c
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@ -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 +