[dpdk-dev] [PATCH] examples/l3fwd: fix TX burst queue drain edge case

Subsystems: the rest

5 messages, 2 authors, 2021-04-20 · open the first message on its own page

[dpdk-dev] [PATCH] examples/l3fwd: fix TX burst queue drain edge case

From: Kathleen Capella <hidden>
Date: 2021-02-23 18:26:25

Initialize prev_tsc to cur_tsc. This avoids running the TX queue drain
in the first iteration of the packet processing loop.

Fixes: af75078fece3 ("first public release")

Signed-off-by: Kathleen Capella <redacted>
Reviewed-by: Honnappa Nagarahalli <redacted>
---
 examples/l3fwd/l3fwd_em.c  | 9 +++++----
 examples/l3fwd/l3fwd_lpm.c | 9 +++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
index 9996bfba3..01f8dff48 100644
--- a/examples/l3fwd/l3fwd_em.c
+++ b/examples/l3fwd/l3fwd_em.c

@@ -629,8 +629,6 @@ em_main_loop(__rte_unused void *dummy)
 	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) /
 		US_PER_S * BURST_TX_DRAIN_US;
 
-	prev_tsc = 0;
-
 	lcore_id = rte_lcore_id();
 	qconf = &lcore_conf[lcore_id];

@@ -650,9 +648,10 @@ em_main_loop(__rte_unused void *dummy)
 			lcore_id, portid, queueid);
 	}
 
-	while (!force_quit) {
+	cur_tsc = rte_rdtsc();
+	prev_tsc = cur_tsc;
 
-		cur_tsc = rte_rdtsc();
+	while (!force_quit) {
 
 		/*
 		 * TX burst queue drain

@@ -692,6 +691,8 @@ em_main_loop(__rte_unused void *dummy)
 							portid, qconf);
 #endif
 		}
+
+		cur_tsc = rte_rdtsc();
 	}
 
 	return 0;

diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
index 3dcf1fef1..375746fef 100644
--- a/examples/l3fwd/l3fwd_lpm.c
+++ b/examples/l3fwd/l3fwd_lpm.c

@@ -185,8 +185,6 @@ lpm_main_loop(__rte_unused void *dummy)
 	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) /
 		US_PER_S * BURST_TX_DRAIN_US;
 
-	prev_tsc = 0;
-
 	lcore_id = rte_lcore_id();
 	qconf = &lcore_conf[lcore_id];

@@ -206,9 +204,10 @@ lpm_main_loop(__rte_unused void *dummy)
 			lcore_id, portid, queueid);
 	}
 
-	while (!force_quit) {
+	cur_tsc = rte_rdtsc();
+	prev_tsc = cur_tsc;
 
-		cur_tsc = rte_rdtsc();
+	while (!force_quit) {
 
 		/*
 		 * TX burst queue drain

@@ -249,6 +248,8 @@ lpm_main_loop(__rte_unused void *dummy)
 							portid, qconf);
 #endif /* X86 */
 		}
+
+		cur_tsc = rte_rdtsc();
 	}
 
 	return 0;

-- 
2.17.1

Re: [dpdk-dev] [PATCH] examples/l3fwd: fix TX burst queue drain edge case

From: Thomas Monjalon <hidden>
Date: 2021-03-24 17:15:45

23/02/2021 19:23, Kathleen Capella:

Initialize prev_tsc to cur_tsc. This avoids running the TX queue drain
in the first iteration of the packet processing loop.

Is it really a fix? What was broken?
Isn't it an optimization?

Fixes: af75078fece3 ("first public release")

If it's really a fix, we should probably backport it, so
Cc: stable@dpdk.org

Signed-off-by: Kathleen Capella <redacted>
Reviewed-by: Honnappa Nagarahalli <redacted>

Re: [dpdk-dev] [PATCH] examples/l3fwd: fix TX burst queue drain edge case

From: Kathleen Capella <hidden>
Date: 2021-03-26 16:28:00

-----Original Message-----
From: Thomas Monjalon <redacted>
Sent: Wednesday, March 24, 2021 1:16 PM
To: Kathleen Capella <redacted>
Cc: dev@dpdk.org; nd <redacted>; Honnappa Nagarahalli
[off-list ref]
Subject: Re: [dpdk-dev] [PATCH] examples/l3fwd: fix TX burst queue drain edge
case

23/02/2021 19:23, Kathleen Capella:

quoted

Initialize prev_tsc to cur_tsc. This avoids running the TX queue drain
in the first iteration of the packet processing loop.

Is it really a fix? What was broken?
Isn't it an optimization?

It could be considered an optimization since effectively it prevents entering the if statement on the
first iteration of the loop. I will remove the "fixes" line and reword the subject line.

quoted

Fixes: af75078fece3 ("first public release")

If it's really a fix, we should probably backport it, so
Cc: stable@dpdk.org

[Kathleen Capella] 
It is not really a significant problem to be fixed in previous releases so it does not need to be backported.

quoted

Signed-off-by: Kathleen Capella <redacted>
Reviewed-by: Honnappa Nagarahalli <redacted>

[dpdk-dev] [PATCH v2] examples/l3fwd: skip TX queue drain on first iteration

From: Kathleen Capella <hidden>
Date: 2021-04-08 21:36:40

Initialize prev_tsc to cur_tsc. This avoids running the TX queue drain
in the first iteration of the packet processing loop.

Signed-off-by: Kathleen Capella <redacted>
Reviewed-by: Honnappa Nagarahalli <redacted>
---
 examples/l3fwd/l3fwd_em.c  | 9 +++++----
 examples/l3fwd/l3fwd_lpm.c | 9 +++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/examples/l3fwd/l3fwd_em.c b/examples/l3fwd/l3fwd_em.c
index 9996bfba3..01f8dff48 100644
--- a/examples/l3fwd/l3fwd_em.c
+++ b/examples/l3fwd/l3fwd_em.c

@@ -629,8 +629,6 @@ em_main_loop(__rte_unused void *dummy)
 	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) /
 		US_PER_S * BURST_TX_DRAIN_US;
 
-	prev_tsc = 0;
-
 	lcore_id = rte_lcore_id();
 	qconf = &lcore_conf[lcore_id];

@@ -650,9 +648,10 @@ em_main_loop(__rte_unused void *dummy)
 			lcore_id, portid, queueid);
 	}
 
-	while (!force_quit) {
+	cur_tsc = rte_rdtsc();
+	prev_tsc = cur_tsc;
 
-		cur_tsc = rte_rdtsc();
+	while (!force_quit) {
 
 		/*
 		 * TX burst queue drain

@@ -692,6 +691,8 @@ em_main_loop(__rte_unused void *dummy)
 							portid, qconf);
 #endif
 		}
+
+		cur_tsc = rte_rdtsc();
 	}
 
 	return 0;

diff --git a/examples/l3fwd/l3fwd_lpm.c b/examples/l3fwd/l3fwd_lpm.c
index 3dcf1fef1..375746fef 100644
--- a/examples/l3fwd/l3fwd_lpm.c
+++ b/examples/l3fwd/l3fwd_lpm.c

@@ -185,8 +185,6 @@ lpm_main_loop(__rte_unused void *dummy)
 	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) /
 		US_PER_S * BURST_TX_DRAIN_US;
 
-	prev_tsc = 0;
-
 	lcore_id = rte_lcore_id();
 	qconf = &lcore_conf[lcore_id];

@@ -206,9 +204,10 @@ lpm_main_loop(__rte_unused void *dummy)
 			lcore_id, portid, queueid);
 	}
 
-	while (!force_quit) {
+	cur_tsc = rte_rdtsc();
+	prev_tsc = cur_tsc;
 
-		cur_tsc = rte_rdtsc();
+	while (!force_quit) {
 
 		/*
 		 * TX burst queue drain

@@ -249,6 +248,8 @@ lpm_main_loop(__rte_unused void *dummy)
 							portid, qconf);
 #endif /* X86 */
 		}
+
+		cur_tsc = rte_rdtsc();
 	}
 
 	return 0;

-- 
2.17.1

Re: [dpdk-dev] [PATCH v2] examples/l3fwd: skip TX queue drain on first iteration

From: Thomas Monjalon <hidden>
Date: 2021-04-20 01:12:21

08/04/2021 23:35, Kathleen Capella:

Initialize prev_tsc to cur_tsc. This avoids running the TX queue drain
in the first iteration of the packet processing loop.

Signed-off-by: Kathleen Capella <redacted>
Reviewed-by: Honnappa Nagarahalli <redacted>

Applied, thanks

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