[ovs-dev] dpif-netdev: move header prefetch earlier into the receive function
diff mbox

Message ID 1442521785-32423-1-git-send-email-zoltan.kiss@linaro.org
State Deferred
Headers show

Commit Message

Zoltan Kiss Sept. 17, 2015, 8:29 p.m. UTC
It's better to have it in the cache as soon as possible. On my test setup it
meant a 0.7 Mpps increase.

Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>

Comments

Daniele Di Proietto Sept. 25, 2015, 4:44 p.m. UTC | #1
I tested the patch, but I wasn't able to reproduce your measurements.

On my test setup I noticed no difference in throughput for different packet
sizes/flow tables.

Could you describe your setup in more details?

I'd be happy to improve prefetching if it a simple change like the this.

Thanks,

Daniele

On 17/09/2015 21:29, "Zoltan Kiss" <zoltan.kiss@linaro.org> wrote:

>It's better to have it in the cache as soon as possible. On my test setup
>it
>meant a 0.7 Mpps increase.
>
>Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>
>
>diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>index 72e5653..3312cc0 100644
>--- a/lib/dpif-netdev.c
>+++ b/lib/dpif-netdev.c
>@@ -3229,11 +3229,6 @@ emc_processing(struct dp_netdev_pmd_thread *pmd,
>struct dp_packet **packets,
>             continue;
>         }
> 
>-        if (i != cnt - 1) {
>-            /* Prefetch next packet data */
>-            OVS_PREFETCH(dp_packet_data(packets[i+1]));
>-        }
>-
>         miniflow_extract(packets[i], &key.mf);
>         key.len = 0; /* Not computed yet. */
>         key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);
>diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>index e4e3d2c..c3c7ec0 100644
>--- a/lib/netdev-dpdk.c
>+++ b/lib/netdev-dpdk.c
>@@ -1015,7 +1015,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,
>struct dp_packet **packets,
>     struct netdev_rxq_dpdk *rx = netdev_rxq_dpdk_cast(rxq_);
>     struct netdev *netdev = rx->up.netdev;
>     struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
>-    int nb_rx;
>+    int nb_rx, i;
> 
>     /* There is only one tx queue for this core.  Do not flush other
>      * queues.
>@@ -1033,6 +1033,9 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,
>struct dp_packet **packets,
>         return EAGAIN;
>     }
> 
>+    for (i = 0; i < nb_rx; i++)
>+        OVS_PREFETCH(dp_packet_data(packets[i]));
>+
>     *c = nb_rx;
> 
>     return 0;
>
>_______________________________________________
>dev mailing list
>dev@openvswitch.org
>https://urldefense.proofpoint.com/v2/url?u=http-3A__openvswitch.org_mailma
>n_listinfo_dev&d=BQIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=Sm
>B5nZacmXNq0gKCC1s_Cw5yUNjxgD4v5kJqZ2uWLlE&m=3RVqArIQwG9h7SC_5ZdxmrRZ3p0soQ
>NTcUPJwi3-ZZA&s=Q9jC4I1Pmb4XizqudZUy0cMZBgHvmlSGcZerBzZW-Ig&e=
Zoltan Kiss Sept. 25, 2015, 6:29 p.m. UTC | #2
Hi,

I've used an Intel 82599ES card with the ixgbe vector PMD. The DPDK 
drivers generally not very consistent about prefetching the header, e.g. 
the other ixgbe receive functions do it, but the vector one doesn't. And 
I used a single flow of 64 bytes UDP packets.

Regards,

Zoltan

On 25/09/15 09:44, Daniele Di Proietto wrote:
> I tested the patch, but I wasn't able to reproduce your measurements.
>
> On my test setup I noticed no difference in throughput for different packet
> sizes/flow tables.
>
> Could you describe your setup in more details?
>
> I'd be happy to improve prefetching if it a simple change like the this.
>
> Thanks,
>
> Daniele
>
> On 17/09/2015 21:29, "Zoltan Kiss" <zoltan.kiss@linaro.org> wrote:
>
>> It's better to have it in the cache as soon as possible. On my test setup
>> it
>> meant a 0.7 Mpps increase.
>>
>> Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>
>>
>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>> index 72e5653..3312cc0 100644
>> --- a/lib/dpif-netdev.c
>> +++ b/lib/dpif-netdev.c
>> @@ -3229,11 +3229,6 @@ emc_processing(struct dp_netdev_pmd_thread *pmd,
>> struct dp_packet **packets,
>>              continue;
>>          }
>>
>> -        if (i != cnt - 1) {
>> -            /* Prefetch next packet data */
>> -            OVS_PREFETCH(dp_packet_data(packets[i+1]));
>> -        }
>> -
>>          miniflow_extract(packets[i], &key.mf);
>>          key.len = 0; /* Not computed yet. */
>>          key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>> index e4e3d2c..c3c7ec0 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -1015,7 +1015,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,
>> struct dp_packet **packets,
>>      struct netdev_rxq_dpdk *rx = netdev_rxq_dpdk_cast(rxq_);
>>      struct netdev *netdev = rx->up.netdev;
>>      struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
>> -    int nb_rx;
>> +    int nb_rx, i;
>>
>>      /* There is only one tx queue for this core.  Do not flush other
>>       * queues.
>> @@ -1033,6 +1033,9 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,
>> struct dp_packet **packets,
>>          return EAGAIN;
>>      }
>>
>> +    for (i = 0; i < nb_rx; i++)
>> +        OVS_PREFETCH(dp_packet_data(packets[i]));
>> +
>>      *c = nb_rx;
>>
>>      return 0;
>>
>> _______________________________________________
>> dev mailing list
>> dev@openvswitch.org
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__openvswitch.org_mailma
>> n_listinfo_dev&d=BQIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=Sm
>> B5nZacmXNq0gKCC1s_Cw5yUNjxgD4v5kJqZ2uWLlE&m=3RVqArIQwG9h7SC_5ZdxmrRZ3p0soQ
>> NTcUPJwi3-ZZA&s=Q9jC4I1Pmb4XizqudZUy0cMZBgHvmlSGcZerBzZW-Ig&e=
Loftus, Ciara Sept. 28, 2015, 12:35 p.m. UTC | #3
> 

> I tested the patch, but I wasn't able to reproduce your measurements.


I was able to reproduce a slight performance improvement with this patch for single-flow uni-directional 64B traffic - up about 0.3Mpps for me.

Thanks,
Ciara

> 

> On my test setup I noticed no difference in throughput for different packet

> sizes/flow tables.

> 

> Could you describe your setup in more details?

> 

> I'd be happy to improve prefetching if it a simple change like the this.

> 

> Thanks,

> 

> Daniele

> 

> On 17/09/2015 21:29, "Zoltan Kiss" <zoltan.kiss@linaro.org> wrote:

> 

> >It's better to have it in the cache as soon as possible. On my test setup

> >it

> >meant a 0.7 Mpps increase.

> >

> >Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>

> >

> >diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c

> >index 72e5653..3312cc0 100644

> >--- a/lib/dpif-netdev.c

> >+++ b/lib/dpif-netdev.c

> >@@ -3229,11 +3229,6 @@ emc_processing(struct dp_netdev_pmd_thread

> *pmd,

> >struct dp_packet **packets,

> >             continue;

> >         }

> >

> >-        if (i != cnt - 1) {

> >-            /* Prefetch next packet data */

> >-            OVS_PREFETCH(dp_packet_data(packets[i+1]));

> >-        }

> >-

> >         miniflow_extract(packets[i], &key.mf);

> >         key.len = 0; /* Not computed yet. */

> >         key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);

> >diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c

> >index e4e3d2c..c3c7ec0 100644

> >--- a/lib/netdev-dpdk.c

> >+++ b/lib/netdev-dpdk.c

> >@@ -1015,7 +1015,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,

> >struct dp_packet **packets,

> >     struct netdev_rxq_dpdk *rx = netdev_rxq_dpdk_cast(rxq_);

> >     struct netdev *netdev = rx->up.netdev;

> >     struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);

> >-    int nb_rx;

> >+    int nb_rx, i;

> >

> >     /* There is only one tx queue for this core.  Do not flush other

> >      * queues.

> >@@ -1033,6 +1033,9 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_,

> >struct dp_packet **packets,

> >         return EAGAIN;

> >     }

> >

> >+    for (i = 0; i < nb_rx; i++)

> >+        OVS_PREFETCH(dp_packet_data(packets[i]));

> >+

> >     *c = nb_rx;

> >

> >     return 0;

> >

> >_______________________________________________

> >dev mailing list

> >dev@openvswitch.org

> >https://urldefense.proofpoint.com/v2/url?u=http-

> 3A__openvswitch.org_mailma

> >n_listinfo_dev&d=BQIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-

> YihVMNtXt-uEs&r=Sm

> >B5nZacmXNq0gKCC1s_Cw5yUNjxgD4v5kJqZ2uWLlE&m=3RVqArIQwG9h7SC

> _5ZdxmrRZ3p0soQ

> >NTcUPJwi3-ZZA&s=Q9jC4I1Pmb4XizqudZUy0cMZBgHvmlSGcZerBzZW-

> Ig&e=

> 

> _______________________________________________

> dev mailing list

> dev@openvswitch.org

> http://openvswitch.org/mailman/listinfo/dev
Flavio Leitner Oct. 13, 2015, 7:01 p.m. UTC | #4
On Thu, Sep 17, 2015 at 09:29:45PM +0100, Zoltan Kiss wrote:
> It's better to have it in the cache as soon as possible. On my test setup it
> meant a 0.7 Mpps increase.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>
> 
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 72e5653..3312cc0 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -3229,11 +3229,6 @@ emc_processing(struct dp_netdev_pmd_thread *pmd, struct dp_packet **packets,
>              continue;
>          }
>  
> -        if (i != cnt - 1) {
> -            /* Prefetch next packet data */
> -            OVS_PREFETCH(dp_packet_data(packets[i+1]));
> -        }
> -
>          miniflow_extract(packets[i], &key.mf);
>          key.len = 0; /* Not computed yet. */
>          key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index e4e3d2c..c3c7ec0 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -1015,7 +1015,7 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet **packets,
>      struct netdev_rxq_dpdk *rx = netdev_rxq_dpdk_cast(rxq_);
>      struct netdev *netdev = rx->up.netdev;
>      struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
> -    int nb_rx;
> +    int nb_rx, i;
>  
>      /* There is only one tx queue for this core.  Do not flush other
>       * queues.
> @@ -1033,6 +1033,9 @@ netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet **packets,
>          return EAGAIN;
>      }
>  
> +    for (i = 0; i < nb_rx; i++)
> +        OVS_PREFETCH(dp_packet_data(packets[i]));
> +

Please use {} even for single statements to follow the coding style.

Do you know if removing the prefetch completely helps?

fbl


>      *c = nb_rx;
>  
>      return 0;
> 
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev

Patch
diff mbox

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 72e5653..3312cc0 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -3229,11 +3229,6 @@  emc_processing(struct dp_netdev_pmd_thread *pmd, struct dp_packet **packets,
             continue;
         }
 
-        if (i != cnt - 1) {
-            /* Prefetch next packet data */
-            OVS_PREFETCH(dp_packet_data(packets[i+1]));
-        }
-
         miniflow_extract(packets[i], &key.mf);
         key.len = 0; /* Not computed yet. */
         key.hash = dpif_netdev_packet_get_rss_hash(packets[i], &key.mf);
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index e4e3d2c..c3c7ec0 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -1015,7 +1015,7 @@  netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet **packets,
     struct netdev_rxq_dpdk *rx = netdev_rxq_dpdk_cast(rxq_);
     struct netdev *netdev = rx->up.netdev;
     struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
-    int nb_rx;
+    int nb_rx, i;
 
     /* There is only one tx queue for this core.  Do not flush other
      * queues.
@@ -1033,6 +1033,9 @@  netdev_dpdk_rxq_recv(struct netdev_rxq *rxq_, struct dp_packet **packets,
         return EAGAIN;
     }
 
+    for (i = 0; i < nb_rx; i++)
+        OVS_PREFETCH(dp_packet_data(packets[i]));
+
     *c = nb_rx;
 
     return 0;