Subject: [RFC PATCH net-next 6/6] net/smc: Introduce tunable linkgroup max connections

From: Tony Lu <[email-masked]>
Date: Fri, 14 Jan 2022 13:48:52 +0800

This introduces tunable sysctl knob max_lgr_conns to tune the max
connections in one linkgroup. This knob is net-namespaceify.

Currently, a linkgroup is shared by SMC_RMBS_PER_LGR_MAX connectiosn at
max, which is 255. This shares one QP, and introduces more competition,
as connections increases, such as smc_cdc_get_free_slot(), it shares
link-level slots. The environment and scenario are different, so this
makes it possible to tunable by users, to save linkgroup resources or
reduce competition and increase performance.

Signed-off-by: Tony Lu <[email-masked]>
---
 include/net/netns/smc.h |  1 +
 net/smc/af_smc.c        |  1 +
 net/smc/smc_core.c      |  2 +-
 net/smc/smc_sysctl.c    | 11 +++++++++++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/net/netns/smc.h b/include/net/netns/smc.h
index f948235e3156..4f55d2876d19 100644
--- a/include/net/netns/smc.h
+++ b/include/net/netns/smc.h
@@ -17,5 +17,6 @@ struct netns_smc {
 #endif
 	int				sysctl_wmem_default;
 	int				sysctl_rmem_default;
+	int				sysctl_max_lgr_conns;
 };
 #endif
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 0650b5971e0a..f38e24cbb4a7 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -2937,6 +2937,7 @@ static __net_init int smc_net_init(struct net *net)
 					   SMC_BUF_MIN_SIZE);
 	net->smc.sysctl_rmem_default = max(net->ipv4.sysctl_tcp_rmem[1],
 					   SMC_BUF_MIN_SIZE);
+	net->smc.sysctl_max_lgr_conns = SMC_RMBS_PER_LGR_MAX;
 
 	return smc_pnet_net_init(net);
 }
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 8935ef4811b0..b6e70dd0688d 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1817,7 +1817,7 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 		    (ini->smcd_version == SMC_V2 ||
 		     lgr->vlan_id == ini->vlan_id) &&
 		    (role == SMC_CLNT || ini->is_smcd ||
-		     lgr->conns_num < SMC_RMBS_PER_LGR_MAX)) {
+		     lgr->conns_num < net->smc.sysctl_max_lgr_conns)) {
 			/* link group found */
 			ini->first_contact_local = 0;
 			conn->lgr = lgr;
diff --git a/net/smc/smc_sysctl.c b/net/smc/smc_sysctl.c
index 6706fe1bd888..5ffcf6008c20 100644
--- a/net/smc/smc_sysctl.c
+++ b/net/smc/smc_sysctl.c
@@ -10,6 +10,8 @@
 
 static int min_sndbuf = SMC_BUF_MIN_SIZE;
 static int min_rcvbuf = SMC_BUF_MIN_SIZE;
+static int min_lgr_conns = 1;
+static int max_lgr_conns = SMC_RMBS_PER_LGR_MAX;
 
 static struct ctl_table smc_table[] = {
 	{
@@ -28,6 +30,15 @@ static struct ctl_table smc_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= &min_rcvbuf,
 	},
+	{
+		.procname	= "max_lgr_conns",
+		.data		= &init_net.smc.sysctl_max_lgr_conns,
+		.maxlen		= sizeof(init_net.smc.sysctl_max_lgr_conns),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &min_lgr_conns,
+		.extra2		= &max_lgr_conns,
+	},
 	{  }
 };
 
-- 
2.32.0.3.g01195cf9f