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authorKuniyuki Iwashima <kuniyu@amazon.com>2022-09-08 04:10:18 +0300
committerJakub Kicinski <kuba@kernel.org>2022-09-20 20:21:49 +0300
commite9bd0cca09d13ac2f08d25e195203e42d4ad1ce8 (patch)
treec098713403c2ed7e70d310348766a1acf9d5e374 /include/net/netns
parent08eaef90403110e51861d93e8008a355af467bbe (diff)
downloadlinux-e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8.tar.xz
tcp: Don't allocate tcp_death_row outside of struct netns_ipv4.
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 fbb8295248e1 ("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 04c494e68a13 ("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>
Diffstat (limited to 'include/net/netns')
-rw-r--r--include/net/netns/ipv4.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 6320a76cefdc..2c7df93e3403 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -34,6 +34,7 @@ struct inet_hashinfo;
struct inet_timewait_death_row {
refcount_t tw_refcount;
+ /* Padding to avoid false sharing, tw_refcount can be often written */
struct inet_hashinfo *hashinfo ____cacheline_aligned_in_smp;
int sysctl_max_tw_buckets;
};
@@ -41,7 +42,7 @@ struct inet_timewait_death_row {
struct tcp_fastopen_context;
struct netns_ipv4 {
- struct inet_timewait_death_row *tcp_death_row;
+ struct inet_timewait_death_row tcp_death_row;
#ifdef CONFIG_SYSCTL
struct ctl_table_header *forw_hdr;