From ede61ca474a0348b975d9824565b66c7595461de Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 14 Jun 2019 16:22:19 -0700
Subject: [PATCH] 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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
Documentation/networking/ip-sysctl.txt | 8 ++++++++
include/net/sock.h | 6 ++----
net/ipv4/sysctl_net_ipv4.c | 9 +++++++++
3 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 14fe93049d28e..288aa264ac26d 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -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
diff --git a/include/net/sock.h b/include/net/sock.h
index e9d769c04637a..b02645e2dfad7 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 875867b64d6a6..886b58d31351d 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -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,
+ },
{ }
};
--
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