Commit d464e84e authored Sep 19, 2017 by Eric Dumazet Committed by David S. Miller Sep 19, 2017

kobject: factorize skb setup in kobject_uevent_net_broadcast()



We can build one skb and let it be cloned in netlink.

This is much faster, and use less memory (all clones will
share the same skb->head)

Tested:

time perf record (for f in `seq 1 3000` ; do ip netns add tast$f; done)
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 4.110 MB perf.data (~179584 samples) ]

real    0m24.227s # instead of 0m52.554s
user    0m0.329s
sys 0m23.753s # instead of 0m51.375s

    14.77%       ip  [kernel.kallsyms]  [k] __ip6addrlbl_add
    14.56%       ip  [kernel.kallsyms]  [k] netlink_broadcast_filtered
    11.65%       ip  [kernel.kallsyms]  [k] netlink_has_listeners
     6.19%       ip  [kernel.kallsyms]  [k] _raw_spin_lock_irqsave
     5.66%       ip  [kernel.kallsyms]  [k] kobject_uevent_env
     4.97%       ip  [kernel.kallsyms]  [k] memset_erms
     4.67%       ip  [kernel.kallsyms]  [k] refcount_sub_and_test
     4.41%       ip  [kernel.kallsyms]  [k] _raw_read_lock
     3.59%       ip  [kernel.kallsyms]  [k] refcount_inc_not_zero
     3.13%       ip  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore
     1.55%       ip  [kernel.kallsyms]  [k] __wake_up
     1.20%       ip  [kernel.kallsyms]  [k] strlen
     1.03%       ip  [kernel.kallsyms]  [k] __wake_up_common
     0.93%       ip  [kernel.kallsyms]  [k] consume_skb
     0.92%       ip  [kernel.kallsyms]  [k] netlink_trim
     0.87%       ip  [kernel.kallsyms]  [k] insert_header
     0.63%       ip  [kernel.kallsyms]  [k] unmap_page_range

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4a336a23

lib/kobject_uevent.c

+19 −15

Original line number	Diff line number	Diff line
		@@ -301,23 +301,26 @@ static int kobject_uevent_net_broadcast(struct kobject *kobj,
		{
		int retval = 0;
		#if defined(CONFIG_NET)
		struct sk_buff *skb = NULL;
		struct uevent_sock *ue_sk;

		/* send netlink message */
		list_for_each_entry(ue_sk, &uevent_sock_list, list) {
		struct sock *uevent_sock = ue_sk->sk;
		struct sk_buff *skb;
		size_t len;

		if (!netlink_has_listeners(uevent_sock, 1))
		continue;

		if (!skb) {
		/* allocate message with the maximum possible size */
		len = strlen(action_string) + strlen(devpath) + 2;
		skb = alloc_skb(len + env->buflen, GFP_KERNEL);
		if (skb) {
		size_t len = strlen(action_string) + strlen(devpath) + 2;
		char *scratch;

		retval = -ENOMEM;
		skb = alloc_skb(len + env->buflen, GFP_KERNEL);
		if (!skb)
		continue;

		/* add header */
		scratch = skb_put(skb, len);
		sprintf(scratch, "%s@%s", action_string, devpath);
		@@ -325,16 +328,17 @@ static int kobject_uevent_net_broadcast(struct kobject *kobj,
		skb_put_data(skb, env->buf, env->buflen);

		NETLINK_CB(skb).dst_group = 1;
		retval = netlink_broadcast_filtered(uevent_sock, skb,
		}

		retval = netlink_broadcast_filtered(uevent_sock, skb_get(skb),
		0, 1, GFP_KERNEL,
		kobj_bcast_filter,
		kobj);
		/* ENOBUFS should be handled in userspace */
		if (retval == -ENOBUFS \|\| retval == -ESRCH)
		retval = 0;
		} else
		retval = -ENOMEM;
		}
		consume_skb(skb);
		#endif
		return retval;
		}