Commit 998642e9 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: move net_cookie into net_aligned_data 



Using per-cpu data for net->net_cookie generation is overkill,
because even busy hosts do not create hundreds of netns per second.

Make sure to put net_cookie in a private cache line to avoid
potential false sharing.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250630093540.3052835-3-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 3715b5df

include/net/aligned_data.h

+2 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#ifndef _NET_ALIGNED_DATA_H

#define _NET_ALIGNED_DATA_H



#include <linux/atomic.h>

#include <linux/types.h>



/* Structure holding cacheline aligned fields on SMP builds.
@@ -9,6 +10,7 @@ 
 * attribute to ensure no accidental false sharing can happen.

 */

struct net_aligned_data {

	atomic64_t	net_cookie ____cacheline_aligned_in_smp;

};



extern struct net_aligned_data net_aligned_data;

net/core/net_namespace.c

+2 −6
Original line number Diff line number Diff line
@@ -19,9 +19,9 @@ 
#include <linux/net_namespace.h>

#include <linux/sched/task.h>

#include <linux/uidgid.h>

#include <linux/cookie.h>

#include <linux/proc_fs.h>



#include <net/aligned_data.h>

#include <net/sock.h>

#include <net/netlink.h>

#include <net/net_namespace.h>
@@ -64,8 +64,6 @@ DECLARE_RWSEM(pernet_ops_rwsem); 


static unsigned int max_gen_ptrs = INITIAL_NET_GEN_PTRS;



DEFINE_COOKIE(net_cookie);



static struct net_generic *net_alloc_generic(void)

{

	unsigned int gen_ptrs = READ_ONCE(max_gen_ptrs);
@@ -434,9 +432,7 @@ static __net_init int setup_net(struct net *net) 
	LIST_HEAD(net_exit_list);

	int error = 0;



	preempt_disable();

	net->net_cookie = gen_cookie_next(&net_cookie);

	preempt_enable();

	net->net_cookie = atomic64_inc_return(&net_aligned_data.net_cookie);



	list_for_each_entry(ops, &pernet_list, list) {

		error = ops_init(ops, net);