[dpdk-stable] [PATCH v2] examples/multi_proces: fix Rx packets distribution

[dpdk-stable] [PATCH v2] examples/multi_proces: fix Rx packets distribution

[Gregory Etelson]

MP servers distributes Rx packets between clients according to
round-robin scheme.

Current implementation always started packets distribution from
the first client. That procedure resulted in uniform distribution
in cases when Rx packets number was around clients number
multiplication. However, if RX burst repeatedly returned single
packet, round-robin scheme would not work because all packets
were assigned to the first client only.

The patch does not restart packets distribution from
the first client.
Packets distribution always continues to the next client.

Cc: stable@dpdk.org

Fixes: af75078fece3 ("first public release")

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
v2: Remove explisit static variable initialization.
---
 examples/multi_process/client_server_mp/mp_server/main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/examples/multi_process/client_server_mp/mp_server/main.c b/examples/multi_process/client_server_mp/mp_server/main.c
index b4761ebc7b..31e7e76706 100644
--- a/examples/multi_process/client_server_mp/mp_server/main.c
+++ b/examples/multi_process/client_server_mp/mp_server/main.c
@@ -234,7 +234,12 @@ process_packets(uint32_t port_num __rte_unused,
 		struct rte_mbuf *pkts[], uint16_t rx_count)
 {
 	uint16_t i;
-	uint8_t client = 0;
+	/*
+	 * C99: All objects with static storage duration
+	 * shall be initialized (set to their initial values) before
+	 * program startup.
+	 */
+	static uint8_t client;
 
 	for (i = 0; i < rx_count; i++) {
 		enqueue_rx_packet(client, pkts[i]);
-- 
2.33.1

Re: [dpdk-stable] [PATCH v2] examples/multi_proces: fix Rx packets distribution

[Thomas Monjalon]

09/11/2021 10:58, Gregory Etelson:
> -	uint8_t client = 0;
> +	/*
> +	 * C99: All objects with static storage duration
> +	 * shall be initialized (set to their initial values) before
> +	 * program startup.
> +	 */

Why adding this comment?

> +	static uint8_t client;

Re: [dpdk-stable] [PATCH v2] examples/multi_proces: fix Rx packets distribution

[Gregory Etelson]

Hello Thomas,

> 09/11/2021 10:58, Gregory Etelson:
> > -     uint8_t client = 0;
> > +     /*
> > +      * C99: All objects with static storage
> duration
> > +      * shall be initialized (set to their initial
> values) before
> > +      * program startup.
> > +      */
> 
> Why adding this comment?
> 
> > +     static uint8_t client;
> 
> 

C99 optimization that was used here is not obvious.
The patch relies on client=0 initialization.
I added the comment to clarify why the client was not initialized.

Re: [dpdk-stable] [PATCH v2] examples/multi_proces: fix Rx packets distribution

[Thomas Monjalon]

09/11/2021 12:49, Gregory Etelson:
> Hello Thomas,
> 
> > 09/11/2021 10:58, Gregory Etelson:
> > > -     uint8_t client = 0;
> > > +     /*
> > > +      * C99: All objects with static storage
> > duration
> > > +      * shall be initialized (set to their initial
> > values) before
> > > +      * program startup.
> > > +      */
> > 
> > Why adding this comment?
> > 
> > > +     static uint8_t client;
> > 
> > 
> 
> C99 optimization that was used here is not obvious.
> The patch relies on client=0 initialization.
> I added the comment to clarify why the client was not initialized.

I think it is the C standard, not only C99.
As far as I know, having static as 0 is obvious for a lot of people.

[PATCH v3] examples/multi_proces: fix Rx packets distribution

[Gregory Etelson]

MP servers distributes Rx packets between clients according to
round-robin scheme.

Current implementation always started packets distribution from
the first client. That procedure resulted in uniform distribution
in cases when Rx packets number was around clients number
multiplication. However, if RX burst repeatedly returned single
packet, round-robin scheme would not work because all packets
were assigned to the first client only.

The patch does not restart packets distribution from
the first client.
Packets distribution always continues to the next client.

Cc: stable@dpdk.org

Fixes: af75078fece3 ("first public release")

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
v2: Remove explisit static variable initialization.
v3: Remove comment.
---
 examples/multi_process/client_server_mp/mp_server/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/multi_process/client_server_mp/mp_server/main.c b/examples/multi_process/client_server_mp/mp_server/main.c
index b4761ebc7b..f54bb8b75a 100644
--- a/examples/multi_process/client_server_mp/mp_server/main.c
+++ b/examples/multi_process/client_server_mp/mp_server/main.c
@@ -234,7 +234,7 @@ process_packets(uint32_t port_num __rte_unused,
 		struct rte_mbuf *pkts[], uint16_t rx_count)
 {
 	uint16_t i;
-	uint8_t client = 0;
+	static uint8_t client;
 
 	for (i = 0; i < rx_count; i++) {
 		enqueue_rx_packet(client, pkts[i]);
-- 
2.33.1

[PATCH v4] examples/multi_process: fix Rx packets distribution

[Gregory Etelson]

MP servers distributes Rx packets between clients according to
round-robin scheme.

Current implementation always started packets distribution from
the first client. That procedure resulted in uniform distribution
in cases when Rx packets number was around clients number
multiplication. However, if RX burst repeatedly returned single
packet, round-robin scheme would not work because all packets
were assigned to the first client only.

The patch does not restart packets distribution from
the first client.
Packets distribution always continues to the next client.

Cc: stable@dpdk.org

Fixes: af75078fece3 ("first public release")

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
v2: Remove explisit static variable initialization.
v3: Remove comment.
v4: Spell check.
---
 examples/multi_process/client_server_mp/mp_server/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/multi_process/client_server_mp/mp_server/main.c b/examples/multi_process/client_server_mp/mp_server/main.c
index b4761ebc7b..f54bb8b75a 100644
--- a/examples/multi_process/client_server_mp/mp_server/main.c
+++ b/examples/multi_process/client_server_mp/mp_server/main.c
@@ -234,7 +234,7 @@ process_packets(uint32_t port_num __rte_unused,
 		struct rte_mbuf *pkts[], uint16_t rx_count)
 {
 	uint16_t i;
-	uint8_t client = 0;
+	static uint8_t client;
 
 	for (i = 0; i < rx_count; i++) {
 		enqueue_rx_packet(client, pkts[i]);
-- 
2.33.1

Re: [PATCH v4] examples/multi_process: fix Rx packets distribution

[David Marchand]

On Wed, Nov 10, 2021 at 5:58 PM Gregory Etelson <getelson@nvidia.com> wrote:
>
> MP servers distributes Rx packets between clients according to
> round-robin scheme.
>
> Current implementation always started packets distribution from
> the first client. That procedure resulted in uniform distribution
> in cases when Rx packets number was around clients number
> multiplication. However, if RX burst repeatedly returned single
> packet, round-robin scheme would not work because all packets
> were assigned to the first client only.
>
> The patch does not restart packets distribution from
> the first client.
> Packets distribution always continues to the next client.
>
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
>
> Signed-off-by: Gregory Etelson <getelson@nvidia.com>
> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

Applied, thanks.


-- 
David Marchand