From b6e811383062f88212082714db849127fa95142c Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Tue, 21 Jun 2022 10:19:10 -0700 Subject: af_unix: Define a per-netns hash table. This commit adds a per netns hash table for AF_UNIX, which size is fixed as UNIX_HASH_SIZE for now. The first implementation defines a per-netns hash table as a single array of lock and list: struct unix_hashbucket { spinlock_t lock; struct hlist_head head; }; struct netns_unix { struct unix_hashbucket *hash; ... }; But, Eric pointed out memory cost that the structure has holes because of sizeof(spinlock_t), which is 4 (or more if LOCKDEP is enabled). [0] It could be expensive on a host with thousands of netns and few AF_UNIX sockets. For this reason, a per-netns hash table uses two dense arrays. struct unix_table { spinlock_t *locks; struct hlist_head *buckets; }; struct netns_unix { struct unix_table table; ... }; Note the length of the list has a significant impact rather than lock contention, so having shared locks can be an option. But, per-netns locks and lists still perform better than the global locks and per-netns lists. [1] Also, this patch adds a change so that struct netns_unix disappears from struct net if CONFIG_UNIX is disabled. [0]: https://lore.kernel.org/netdev/CANn89iLVxO5aqx16azNU7p7Z-nz5NrnM5QTqOzueVxEnkVTxyg@mail.gmail.com/ [1]: https://lore.kernel.org/netdev/20220617175215.1769-1-kuniyu@amazon.com/ Signed-off-by: Kuniyuki Iwashima Signed-off-by: David S. Miller --- include/net/netns/unix.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/net/netns/unix.h') diff --git a/include/net/netns/unix.h b/include/net/netns/unix.h index 91a3d7e39198..6f1a33df061d 100644 --- a/include/net/netns/unix.h +++ b/include/net/netns/unix.h @@ -5,8 +5,14 @@ #ifndef __NETNS_UNIX_H__ #define __NETNS_UNIX_H__ +struct unix_table { + spinlock_t *locks; + struct hlist_head *buckets; +}; + struct ctl_table_header; struct netns_unix { + struct unix_table table; int sysctl_max_dgram_qlen; struct ctl_table_header *ctl; }; -- cgit