b6e8113830
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 <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
21 lines
363 B
C
21 lines
363 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Unix network namespace
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*/
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#ifndef __NETNS_UNIX_H__
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#define __NETNS_UNIX_H__
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struct unix_table {
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spinlock_t *locks;
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struct hlist_head *buckets;
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};
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struct ctl_table_header;
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struct netns_unix {
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struct unix_table table;
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int sysctl_max_dgram_qlen;
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struct ctl_table_header *ctl;
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};
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#endif /* __NETNS_UNIX_H__ */
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