netdev - [PATCH net-next 6/7] net/smc: don't req

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220301094402.14992-7-dust.li@linux.alibaba.com>
Date:   Tue,  1 Mar 2022 17:44:01 +0800
From:   Dust Li <dust.li@...ux.alibaba.com>
To:     Karsten Graul <kgraul@...ux.ibm.com>,
        Tony Lu <tonylu@...ux.alibaba.com>,
        Guangguan Wang <guangguan.wang@...ux.alibaba.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: [PATCH net-next 6/7] net/smc: don't req_notify until all CQEs drained

When we are handling softirq workload, enable hardirq may
again interrupt the current routine of softirq, and then
try to raise softirq again. This only wastes CPU cycles
and won't have any real gain.

Since IB_CQ_REPORT_MISSED_EVENTS already make sure if
ib_req_notify_cq() returns 0, it is safe to wait for the
next event, with no need to poll the CQ again in this case.

This patch disables hardirq during the processing of softirq,
and re-arm the CQ after softirq is done. Somehow like NAPI.

Co-developed-by: Guangguan Wang <guangguan.wang@...ux.alibaba.com>
Signed-off-by: Guangguan Wang <guangguan.wang@...ux.alibaba.com>
Signed-off-by: Dust Li <dust.li@...ux.alibaba.com>
---
 net/smc/smc_wr.c | 49 +++++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 21 deletions(-)

diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c
index 24be1d03fef9..34d616406d51 100644
--- a/net/smc/smc_wr.c
+++ b/net/smc/smc_wr.c
@@ -137,25 +137,28 @@ static void smc_wr_tx_tasklet_fn(struct tasklet_struct *t)
 {
 	struct smc_ib_device *dev = from_tasklet(dev, t, send_tasklet);
 	struct ib_wc wc[SMC_WR_MAX_POLL_CQE];
-	int i = 0, rc;
-	int polled = 0;
+	int i, rc;
 
 again:
-	polled++;
 	do {
 		memset(&wc, 0, sizeof(wc));
 		rc = ib_poll_cq(dev->roce_cq_send, SMC_WR_MAX_POLL_CQE, wc);
-		if (polled == 1) {
-			ib_req_notify_cq(dev->roce_cq_send,
-					 IB_CQ_NEXT_COMP |
-					 IB_CQ_REPORT_MISSED_EVENTS);
-		}
-		if (!rc)
-			break;
 		for (i = 0; i < rc; i++)
 			smc_wr_tx_process_cqe(&wc[i]);
+		if (rc < SMC_WR_MAX_POLL_CQE)
+			/* If < SMC_WR_MAX_POLL_CQE, the CQ should have been
+			 * drained, no need to poll again. --Guangguan Wang
+			 */
+			break;
 	} while (rc > 0);
-	if (polled == 1)
+
+	/* IB_CQ_REPORT_MISSED_EVENTS make sure if ib_req_notify_cq() returns
+	 * 0, it is safe to wait for the next event.
+	 * Else we must poll the CQ again to make sure we won't miss any event
+	 */
+	if (ib_req_notify_cq(dev->roce_cq_send,
+			     IB_CQ_NEXT_COMP |
+			     IB_CQ_REPORT_MISSED_EVENTS))
 		goto again;
 }
 
@@ -478,24 +481,28 @@ static void smc_wr_rx_tasklet_fn(struct tasklet_struct *t)
 {
 	struct smc_ib_device *dev = from_tasklet(dev, t, recv_tasklet);
 	struct ib_wc wc[SMC_WR_MAX_POLL_CQE];
-	int polled = 0;
 	int rc;
 
 again:
-	polled++;
 	do {
 		memset(&wc, 0, sizeof(wc));
 		rc = ib_poll_cq(dev->roce_cq_recv, SMC_WR_MAX_POLL_CQE, wc);
-		if (polled == 1) {
-			ib_req_notify_cq(dev->roce_cq_recv,
-					 IB_CQ_SOLICITED_MASK
-					 | IB_CQ_REPORT_MISSED_EVENTS);
-		}
-		if (!rc)
+		if (rc > 0)
+			smc_wr_rx_process_cqes(&wc[0], rc);
+		if (rc < SMC_WR_MAX_POLL_CQE)
+			/* If < SMC_WR_MAX_POLL_CQE, the CQ should have been
+			 * drained, no need to poll again. --Guangguan Wang
+			 */
 			break;
-		smc_wr_rx_process_cqes(&wc[0], rc);
 	} while (rc > 0);
-	if (polled == 1)
+
+	/* IB_CQ_REPORT_MISSED_EVENTS make sure if ib_req_notify_cq() returns
+	 * 0, it is safe to wait for the next event.
+	 * Else we must poll the CQ again to make sure we won't miss any event
+	 */
+	if (ib_req_notify_cq(dev->roce_cq_recv,
+			     IB_CQ_SOLICITED_MASK |
+			     IB_CQ_REPORT_MISSED_EVENTS))
 		goto again;
 }
 
-- 
2.19.1.3.ge56e4f7