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tcp: Don't allocate tcp_death_row outside of struct netns_ipv4.

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We will soon introduce an optional per-netns ehash and access hash
tables via net->ipv4.tcp_death_row->hashinfo instead of &tcp_hashinfo
in most places.

It could harm the fast path because dereferences of two fields in net
and tcp_death_row might incur two extra cache line misses.  To save one
dereference, let's place tcp_death_row back in netns_ipv4 and fetch
hashinfo via net->ipv4.tcp_death_row"."hashinfo.

Note tcp_death_row was initially placed in netns_ipv4, and commit
fbb8295248 ("tcp: allocate tcp_death_row outside of struct netns_ipv4")
changed it to a pointer so that we can fire TIME_WAIT timers after freeing
net.  However, we don't do so after commit 04c494e68a ("Revert "tcp/dccp:
get rid of inet_twsk_purge()""), so we need not define tcp_death_row as a
pointer.

Also, we move refcount_dec_and_test(&tw_refcount) from tcp_sk_exit() to
tcp_sk_exit_batch() as a debug check.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2022-09-07 18:10:18 -07:00
committed by Jakub Kicinski
parent 08eaef9040
commit e9bd0cca09
7 changed files with 15 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
net/ipv4/tcp_ipv4.c
View File

@@ -292,7 +292,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
* complete initialization after this.
*/
tcp_set_state(sk, TCP_SYN_SENT);
tcp_death_row = net->ipv4.tcp_death_row;
tcp_death_row = &net->ipv4.tcp_death_row;
err = inet_hash_connect(tcp_death_row, sk);
if (err)
goto failure;
@@ -3091,13 +3091,9 @@ EXPORT_SYMBOL(tcp_prot);
static void __net_exit tcp_sk_exit(struct net *net)
{
struct inet_timewait_death_row *tcp_death_row = net->ipv4.tcp_death_row;
if (net->ipv4.tcp_congestion_control)
bpf_module_put(net->ipv4.tcp_congestion_control,
net->ipv4.tcp_congestion_control->owner);
if (refcount_dec_and_test(&tcp_death_row->tw_refcount))
kfree(tcp_death_row);
}
static int __net_init tcp_sk_init(struct net *net)
@@ -3129,13 +3125,10 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_tw_reuse = 2;
net->ipv4.sysctl_tcp_no_ssthresh_metrics_save = 1;
net->ipv4.tcp_death_row = kzalloc(sizeof(struct inet_timewait_death_row), GFP_KERNEL);
if (!net->ipv4.tcp_death_row)
return -ENOMEM;
refcount_set(&net->ipv4.tcp_death_row->tw_refcount, 1);
refcount_set(&net->ipv4.tcp_death_row.tw_refcount, 1);
cnt = tcp_hashinfo.ehash_mask + 1;
net->ipv4.tcp_death_row->sysctl_max_tw_buckets = cnt / 2;
net->ipv4.tcp_death_row->hashinfo = &tcp_hashinfo;
net->ipv4.tcp_death_row.sysctl_max_tw_buckets = cnt / 2;
net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo;
net->ipv4.sysctl_max_syn_backlog = max(128, cnt / 128);
net->ipv4.sysctl_tcp_sack = 1;
@@ -3201,8 +3194,10 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
inet_twsk_purge(&tcp_hashinfo, AF_INET);
list_for_each_entry(net, net_exit_list, exit_list)
list_for_each_entry(net, net_exit_list, exit_list) {
WARN_ON_ONCE(!refcount_dec_and_test(&net->ipv4.tcp_death_row.tw_refcount));
tcp_fastopen_ctx_destroy(net);
}
}
static struct pernet_operations __net_initdata tcp_sk_ops = {