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net: add skb_defer_disable_key static key

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Add a static key to bypass skb_attempt_defer_free() steps
if net.core.skb_defer_max is set to zero.

Main benefit is the atomic_long_inc_return() avoidance.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260311191340.1996888-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-03-11 19:13:40 +00:00 committed by Jakub Kicinski
parent 15abbe7c82
commit 08dc30de1a
3 changed files with 30 additions and 1 deletions
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1
net/core/net-sysfs.h
View File

@ -13,4 +13,5 @@ int netdev_change_owner(struct net_device *, const struct net *net_old,
extern struct mutex rps_default_mask_mutex;
DECLARE_STATIC_KEY_FALSE(skb_defer_disable_key);
#endif

5
net/core/skbuff.c
View File

@ -7256,6 +7256,8 @@ static void kfree_skb_napi_cache(struct sk_buff *skb)
local_bh_enable();
}
DEFINE_STATIC_KEY_FALSE(skb_defer_disable_key);
/**
* skb_attempt_defer_free - queue skb for remote freeing
* @skb: buffer
@ -7272,6 +7274,9 @@ void skb_attempt_defer_free(struct sk_buff *skb)
bool kick;
int cpu;
if (static_branch_unlikely(&skb_defer_disable_key))
goto nodefer;
/* zero copy notifications should not be delayed. */
if (skb_zcopy(skb))
goto nodefer;

25
net/core/sysctl_net_core.c
View File

@ -349,6 +349,29 @@ static int proc_do_rss_key(const struct ctl_table *table, int write,
return proc_dostring(&fake_table, write, buffer, lenp, ppos);
}
static int proc_do_skb_defer_max(const struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
static DEFINE_MUTEX(skb_defer_max_mutex);
int ret, oval, nval;
mutex_lock(&skb_defer_max_mutex);
oval = !net_hotdata.sysctl_skb_defer_max;
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
nval = !net_hotdata.sysctl_skb_defer_max;
if (nval != oval) {
if (nval)
static_branch_enable(&skb_defer_disable_key);
else
static_branch_disable(&skb_defer_disable_key);
}
mutex_unlock(&skb_defer_max_mutex);
return ret;
}
#ifdef CONFIG_BPF_JIT
static int proc_dointvec_minmax_bpf_enable(const struct ctl_table *table, int write,
void *buffer, size_t *lenp,
@ -650,7 +673,7 @@ static struct ctl_table net_core_table[] = {
.data = &net_hotdata.sysctl_skb_defer_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.proc_handler = proc_do_skb_defer_max,
.extra1 = SYSCTL_ZERO,
},
};