tcp: convert elligible sysctls to u8

[ Upstream commit 4ecc1ba ]

Many tcp sysctls are either bools or small ints that can fit into u8.

Reducing space taken by sysctls can save few cache line misses
when sending/receiving data while cpu caches are empty,
for example after cpu idle period.

This is hard to measure with typical network performance tests,
but after this patch, struct netns_ipv4 has shrunk
by three cache lines.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: dc5110c ("tcp: restrict net.ipv4.tcp_app_win")
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/net/netns/ipv4.h

@@ -114,58 +114,59 @@ struct netns_ipv4 {
 	u8 sysctl_nexthop_compat_mode;
 
 	u8 sysctl_fwmark_reflect;
-	int sysctl_tcp_fwmark_accept;
+	u8 sysctl_tcp_fwmark_accept;
 #ifdef CONFIG_NET_L3_MASTER_DEV
-	int sysctl_tcp_l3mdev_accept;
+	u8 sysctl_tcp_l3mdev_accept;
 #endif
-	int sysctl_tcp_mtu_probing;
+	u8 sysctl_tcp_mtu_probing;
 	int sysctl_tcp_mtu_probe_floor;
 	int sysctl_tcp_base_mss;
 	int sysctl_tcp_min_snd_mss;
 	int sysctl_tcp_probe_threshold;
 	u32 sysctl_tcp_probe_interval;
 
 	int sysctl_tcp_keepalive_time;
-	int sysctl_tcp_keepalive_probes;
 	int sysctl_tcp_keepalive_intvl;
+	u8 sysctl_tcp_keepalive_probes;
 
-	int sysctl_tcp_syn_retries;
-	int sysctl_tcp_synack_retries;
-	int sysctl_tcp_syncookies;
+	u8 sysctl_tcp_syn_retries;
+	u8 sysctl_tcp_synack_retries;
+	u8 sysctl_tcp_syncookies;
 	int sysctl_tcp_reordering;
-	int sysctl_tcp_retries1;
-	int sysctl_tcp_retries2;
-	int sysctl_tcp_orphan_retries;
+	u8 sysctl_tcp_retries1;
+	u8 sysctl_tcp_retries2;
+	u8 sysctl_tcp_orphan_retries;
+	u8 sysctl_tcp_tw_reuse;
 	int sysctl_tcp_fin_timeout;
 	unsigned int sysctl_tcp_notsent_lowat;
-	int sysctl_tcp_tw_reuse;
-	int sysctl_tcp_sack;
-	int sysctl_tcp_window_scaling;
-	int sysctl_tcp_timestamps;
-	int sysctl_tcp_early_retrans;
-	int sysctl_tcp_recovery;
-	int sysctl_tcp_thin_linear_timeouts;
-	int sysctl_tcp_slow_start_after_idle;
-	int sysctl_tcp_retrans_collapse;
-	int sysctl_tcp_stdurg;
-	int sysctl_tcp_rfc1337;
-	int sysctl_tcp_abort_on_overflow;
-	int sysctl_tcp_fack;
+	u8 sysctl_tcp_sack;
+	u8 sysctl_tcp_window_scaling;
+	u8 sysctl_tcp_timestamps;
+	u8 sysctl_tcp_early_retrans;
+	u8 sysctl_tcp_recovery;
+	u8 sysctl_tcp_thin_linear_timeouts;
+	u8 sysctl_tcp_slow_start_after_idle;
+	u8 sysctl_tcp_retrans_collapse;
+	u8 sysctl_tcp_stdurg;
+	u8 sysctl_tcp_rfc1337;
+	u8 sysctl_tcp_abort_on_overflow;
+	u8 sysctl_tcp_fack; /* obsolete */
 	int sysctl_tcp_max_reordering;
-	int sysctl_tcp_dsack;
-	int sysctl_tcp_app_win;
 	int sysctl_tcp_adv_win_scale;
-	int sysctl_tcp_frto;
-	int sysctl_tcp_nometrics_save;
-	int sysctl_tcp_no_ssthresh_metrics_save;
-	int sysctl_tcp_moderate_rcvbuf;
-	int sysctl_tcp_tso_win_divisor;
-	int sysctl_tcp_workaround_signed_windows;
+	u8 sysctl_tcp_dsack;
+	u8 sysctl_tcp_app_win;
+	u8 sysctl_tcp_frto;
+	u8 sysctl_tcp_nometrics_save;
+	u8 sysctl_tcp_no_ssthresh_metrics_save;
+	u8 sysctl_tcp_moderate_rcvbuf;
+	u8 sysctl_tcp_tso_win_divisor;
+	u8 sysctl_tcp_workaround_signed_windows;
 	int sysctl_tcp_limit_output_bytes;
 	int sysctl_tcp_challenge_ack_limit;
-	int sysctl_tcp_min_tso_segs;
 	int sysctl_tcp_min_rtt_wlen;
-	int sysctl_tcp_autocorking;
+	u8 sysctl_tcp_min_tso_segs;
+	u8 sysctl_tcp_autocorking;
+	u8 sysctl_tcp_reflect_tos;
 	int sysctl_tcp_invalid_ratelimit;
 	int sysctl_tcp_pacing_ss_ratio;
 	int sysctl_tcp_pacing_ca_ratio;
@@ -183,7 +184,6 @@ struct netns_ipv4 {
 	unsigned int sysctl_tcp_fastopen_blackhole_timeout;
 	atomic_t tfo_active_disable_times;
 	unsigned long tfo_active_disable_stamp;
-	int sysctl_tcp_reflect_tos;
 
 	int sysctl_udp_wmem_min;
 	int sysctl_udp_rmem_min;