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Commit ede61ca4 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: add tcp_rx_skb_cache sysctl 



Instead of relying on rps_needed, it is safer to use a separate
static key, since we do not want to enable TCP rx_skb_cache
by default. This feature can cause huge increase of memory
usage on hosts with millions of sockets.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a8e11e5c

Documentation/networking/ip-sysctl.txt

+8 −0
Original line number Diff line number Diff line
@@ -772,6 +772,14 @@ tcp_challenge_ack_limit - INTEGER 
	in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)

	Default: 100



tcp_rx_skb_cache - BOOLEAN

	Controls a per TCP socket cache of one skb, that might help

	performance of some workloads. This might be dangerous

	on systems with a lot of TCP sockets, since it increases

	memory usage.



	Default: 0 (disabled)



UDP variables:



udp_l3mdev_accept - BOOLEAN

include/net/sock.h

+2 −4
Original line number Diff line number Diff line
@@ -2433,13 +2433,11 @@ static inline void skb_setup_tx_timestamp(struct sk_buff *skb, __u16 tsflags) 
 * This routine must be called with interrupts disabled or with the socket

 * locked so that the sk_buff queue operation is ok.

*/

DECLARE_STATIC_KEY_FALSE(tcp_rx_skb_cache_key);

static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb)

{

	__skb_unlink(skb, &sk->sk_receive_queue);

	if (

#ifdef CONFIG_RPS

	    !static_branch_unlikely(&rps_needed) &&

#endif

	if (static_branch_unlikely(&tcp_rx_skb_cache_key) &&

	    !sk->sk_rx_skb_cache) {

		sk->sk_rx_skb_cache = skb;

		skb_orphan(skb);

net/ipv4/sysctl_net_ipv4.c

+9 −0
Original line number Diff line number Diff line
@@ -51,6 +51,9 @@ static int comp_sack_nr_max = 255; 
static u32 u32_max_div_HZ = UINT_MAX / HZ;

static int one_day_secs = 24 * 3600;



DEFINE_STATIC_KEY_FALSE(tcp_rx_skb_cache_key);

EXPORT_SYMBOL(tcp_rx_skb_cache_key);



/* obsolete */

static int sysctl_tcp_low_latency __read_mostly;
@@ -559,6 +562,12 @@ static struct ctl_table ipv4_table[] = { 
		.extra1		= &sysctl_fib_sync_mem_min,

		.extra2		= &sysctl_fib_sync_mem_max,

	},

	{

		.procname	= "tcp_rx_skb_cache",

		.data		= &tcp_rx_skb_cache_key.key,

		.mode		= 0644,

		.proc_handler	= proc_do_static_key,

	},

	{ }

};