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| author | Eric Dumazet <edumazet@google.com> | 2021-03-31 20:52:05 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-04-01 00:48:19 +0300 |
| commit | 1caf8d39c58f3f63193d02928c8dce3fa07cee52 (patch) | |
| tree | 831b04bb25e9cedc00c8d16355cde2c673da23e5 /include/net/netns/ipv4.h | |
| parent | 30b8817f5f7a66151b7b772cb9a216706494aa2e (diff) | |
| download | linux-1caf8d39c58f3f63193d02928c8dce3fa07cee52.tar.xz | |
inet: shrink inet_timewait_death_row by 48 bytes
struct inet_timewait_death_row uses two cache lines, because we want
tw_count to use a full cache line to avoid false sharing.
Rework its definition and placement in netns_ipv4 so that:
1) We add 60 bytes of padding after tw_count to avoid
false sharing, knowing that tcp_death_row will
have ____cacheline_aligned_in_smp attribute.
2) We do not risk padding before tcp_death_row, because
we move it at the beginning of netns_ipv4, even if new
fields are added later.
3) We do not waste 48 bytes of padding after it.
Note that I have not changed dccp.
pahole result for struct netns_ipv4 before/after the patch :
/* size: 832, cachelines: 13, members: 139 */
/* sum members: 721, holes: 12, sum holes: 95 */
/* padding: 16 */
/* paddings: 2, sum paddings: 55 */
->
/* size: 768, cachelines: 12, members: 139 */
/* sum members: 673, holes: 11, sum holes: 39 */
/* padding: 56 */
/* paddings: 2, sum paddings: 7 */
/* forced alignments: 1 */
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/netns/ipv4.h')
| -rw-r--r-- | include/net/netns/ipv4.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 9c8dd424d79b..1085ed4e0788 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -32,14 +32,18 @@ struct inet_hashinfo; struct inet_timewait_death_row { atomic_t tw_count; + char tw_pad[L1_CACHE_BYTES - sizeof(atomic_t)]; - struct inet_hashinfo *hashinfo ____cacheline_aligned_in_smp; + struct inet_hashinfo *hashinfo; int sysctl_max_tw_buckets; }; struct tcp_fastopen_context; struct netns_ipv4 { + /* Please keep tcp_death_row at first field in netns_ipv4 */ + struct inet_timewait_death_row tcp_death_row ____cacheline_aligned_in_smp; + #ifdef CONFIG_SYSCTL struct ctl_table_header *forw_hdr; struct ctl_table_header *frags_hdr; @@ -175,7 +179,6 @@ struct netns_ipv4 { int sysctl_tcp_comp_sack_nr; unsigned long sysctl_tcp_comp_sack_delay_ns; unsigned long sysctl_tcp_comp_sack_slack_ns; - struct inet_timewait_death_row tcp_death_row; int sysctl_max_syn_backlog; int sysctl_tcp_fastopen; const struct tcp_congestion_ops __rcu *tcp_congestion_control; |