@@ -1951,8 +1951,8 @@ static bool smcd_lgr_match(struct smc_link_group *lgr,
return true;
}
-/* create a new SMC connection (and a new link group if necessary) */
-int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
+static int __smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini,
+ bool unlock_with_existed_lgr)
{
struct smc_connection *conn = &smc->conn;
struct net *net = sock_net(&smc->sk);
@@ -2026,7 +2026,10 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
smc_lgr_cleanup_early(lgr);
goto out;
}
+ } else if (unlock_with_existed_lgr) {
+ smc_lgr_pending_unlock(ini);
}
+
smc_lgr_hold(conn->lgr); /* lgr_put in smc_conn_free() */
if (!conn->lgr->is_smcd)
smcr_link_hold(conn->lnk); /* link_put in smc_conn_free() */
@@ -2050,6 +2053,16 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
return rc;
}
+/* create a new SMC connection (and a new link group if necessary) */
+int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
+{
+ /* Considering that the path for SMC-D is shorter than SMC-R
+ * the impact of global locking is smaller. So, let's make no
+ * change on SMC-D.
+ */
+ return __smc_conn_create(smc, ini, !ini->is_smcd);
+}
+
#define SMCD_DMBE_SIZES 6 /* 0 -> 16KB, 1 -> 32KB, .. 6 -> 1MB */
#define SMCR_RMBE_SIZES 15 /* 0 -> 16KB, 1 -> 32KB, .. 15 -> 512MB */
To reduce locks scope of smc_xxx_lgr_pending, who aim to serialize the creation of link group. However, once link group existed already, those locks are meaningless, worse still, they make incoming connections have to be queued one after the other. As an optimization, Once we found that we have reused an existing link group, we can immediately release the lock. This way, only the first contact connection needs to hold the global lock throughout its entire lifecycle, while the NON first contact only needing to hold it until the end of smc_conn_create. This greatly alleviates the bottleneck of establishing connections in SMC. Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> --- net/smc/smc_core.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)