Commit f5a5589c authored by Wei Wang's avatar Wei Wang Committed by Jakub Kicinski
Browse files

tcp: use a smaller percpu_counter batch size for sk_alloc 



Currently, a percpu_counter with the default batch size (2*nr_cpus) is
used to record the total # of active sockets per protocol. This means
sk_sockets_allocated_read_positive() could be off by +/-2*(nr_cpus^2).
This under/over-estimation could lead to wrong memory suppression
conditions in __sk_raise_mem_allocated().
Fix this by using a more reasonable fixed batch size of 16.

See related commit cf86a086 ("net/dst: use a smaller percpu_counter
batch for dst entries accounting") that addresses a similar issue.

Signed-off-by: default avatarWei Wang <weiwan@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Link: https://lore.kernel.org/r/20210202193408.1171634-1-weiwan@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 6fd5eeee

include/net/sock.h

+6 −2
Original line number Diff line number Diff line
@@ -1350,14 +1350,18 @@ sk_memory_allocated_sub(struct sock *sk, int amt) 
	atomic_long_sub(amt, sk->sk_prot->memory_allocated);

}



#define SK_ALLOC_PERCPU_COUNTER_BATCH 16



static inline void sk_sockets_allocated_dec(struct sock *sk)

{

	percpu_counter_dec(sk->sk_prot->sockets_allocated);

	percpu_counter_add_batch(sk->sk_prot->sockets_allocated, -1,

				 SK_ALLOC_PERCPU_COUNTER_BATCH);

}



static inline void sk_sockets_allocated_inc(struct sock *sk)

{

	percpu_counter_inc(sk->sk_prot->sockets_allocated);

	percpu_counter_add_batch(sk->sk_prot->sockets_allocated, 1,

				 SK_ALLOC_PERCPU_COUNTER_BATCH);

}



static inline u64