[PATCH net-next v5 1/5] net/smc: Make smc_tcp_listen_work() independent

D. Wythe
2022-02-08T13:16:10Z

From: "D. Wythe" <alibuda@linux.alibaba.com>

In multithread and 10K connections benchmark, the backend TCP connection
established very slowly, and lots of TCP connections stay in SYN_SENT
state.

Client: smc_run wrk -c 10000 -t 4 http://server

the netstate of server host shows like:
145042 times the listen queue of a socket overflowed
145042 SYNs to LISTEN sockets dropped

One reason of this issue is that, since the smc_tcp_listen_work() shared
the same workqueue (smc_hs_wq) with smc_listen_work(), while the
smc_listen_work() do blocking wait for smc connection established. Once
the workqueue became congested, it's will block the accept() from TCP
listen.

This patch creates a independent workqueue(smc_tcp_ls_wq) for
smc_tcp_listen_work(), separate it from smc_listen_work(), which is
quite acceptable considering that smc_tcp_listen_work() runs very fast.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
net/smc/af_smc.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 00b2e9d..4969ac8 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -59,6 +59,7 @@
* creation on client
*/

+static struct workqueue_struct *smc_tcp_ls_wq; /* wq for tcp listen work */
struct workqueue_struct *smc_hs_wq; /* wq for handshake work */
struct workqueue_struct *smc_close_wq; /* wq for close work */

@@ -2227,7 +2228,7 @@ static void smc_clcsock_data_ready(struct sock *listen_clcsock)
lsmc->clcsk_data_ready(listen_clcsock);
if (lsmc->sk.sk_state == SMC_LISTEN) {
sock_hold(&lsmc->sk); /* sock_put in smc_tcp_listen_work() */
- if (!queue_work(smc_hs_wq, &lsmc->tcp_listen_work))
+ if (!queue_work(smc_tcp_ls_wq, &lsmc->tcp_listen_work))
sock_put(&lsmc->sk);
}
}
@@ -3024,9 +3025,14 @@ static int __init smc_init(void)
goto out_nl;

rc = -ENOMEM;
+
+ smc_tcp_ls_wq = alloc_workqueue("smc_tcp_ls_wq", 0, 0);
+ if (!smc_tcp_ls_wq)
+ goto out_pnet;
+
smc_hs_wq = alloc_workqueue("smc_hs_wq", 0, 0);
if (!smc_hs_wq)
- goto out_pnet;
+ goto out_alloc_tcp_ls_wq;

smc_close_wq = alloc_workqueue("smc_close_wq", 0, 0);
if (!smc_close_wq)
@@ -3097,6 +3103,8 @@ static int __init smc_init(void)
destroy_workqueue(smc_close_wq);
out_alloc_hs_wq:
destroy_workqueue(smc_hs_wq);
+out_alloc_tcp_ls_wq:
+ destroy_workqueue(smc_tcp_ls_wq);
out_pnet:
smc_pnet_exit();
out_nl:
@@ -3115,6 +3123,7 @@ static void __exit smc_exit(void)
smc_core_exit();
smc_ib_unregister_client();
destroy_workqueue(smc_close_wq);
+ destroy_workqueue(smc_tcp_ls_wq);
destroy_workqueue(smc_hs_wq);
proto_unregister(&smc_proto6);
proto_unregister(&smc_proto);
--
1.8.3.1