net/af_packet: cache align Rx/Tx structs
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Commit Message
Cache align Rx and Tx queue struct to avoid false sharing.
RX struct happens to be 64 bytes on x86_64 already, so cache alignment
has no effect there, but it does on 32-bit ISAs.
TX struct is 56 bytes on x86_64.
Both structs keep counters, and in the RX case they are updated even
for empty polls.
Fixes: 364e08f2bbc0 ("af_packet: add PMD for AF_PACKET-based virtual devices")
Cc: stable@dpdk.org
Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
---
drivers/net/af_packet/rte_eth_af_packet.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
Comments
On 4/26/2024 8:38 AM, Mattias Rönnblom wrote:
> Cache align Rx and Tx queue struct to avoid false sharing.
>
> RX struct happens to be 64 bytes on x86_64 already, so cache alignment
> has no effect there, but it does on 32-bit ISAs.
>
> TX struct is 56 bytes on x86_64.
>
> Both structs keep counters, and in the RX case they are updated even
> for empty polls.
>
> Fixes: 364e08f2bbc0 ("af_packet: add PMD for AF_PACKET-based virtual devices")
> Cc: stable@dpdk.org
>
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> ---
> drivers/net/af_packet/rte_eth_af_packet.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c
> index 397a32db58..28aeb7d08e 100644
> --- a/drivers/net/af_packet/rte_eth_af_packet.c
> +++ b/drivers/net/af_packet/rte_eth_af_packet.c
> @@ -6,6 +6,7 @@
> * All rights reserved.
> */
>
> +#include <rte_common.h>
> #include <rte_string_fns.h>
> #include <rte_mbuf.h>
> #include <ethdev_driver.h>
> @@ -53,7 +54,7 @@ struct pkt_rx_queue {
>
> volatile unsigned long rx_pkts;
> volatile unsigned long rx_bytes;
> -};
> +} __rte_cache_aligned;
>
> struct pkt_tx_queue {
> int sockfd;
> @@ -67,7 +68,7 @@ struct pkt_tx_queue {
> volatile unsigned long tx_pkts;
> volatile unsigned long err_pkts;
> volatile unsigned long tx_bytes;
> -};
> +} __rte_cache_aligned;
>
> struct pmd_internals {
> unsigned nb_queues;
Hi Mattias,
I guess my comment missed, location of '__rte_cache_aligned' tag changed
for MSVC support, it should be like:
```
struct __rte_cache_aligned pkt_rx_queue {
...
};
```
On 2024-04-26 10:27, Ferruh Yigit wrote:
> On 4/26/2024 8:38 AM, Mattias Rönnblom wrote:
>> Cache align Rx and Tx queue struct to avoid false sharing.
>>
>> RX struct happens to be 64 bytes on x86_64 already, so cache alignment
>> has no effect there, but it does on 32-bit ISAs.
>>
>> TX struct is 56 bytes on x86_64.
>>
>> Both structs keep counters, and in the RX case they are updated even
>> for empty polls.
>>
>> Fixes: 364e08f2bbc0 ("af_packet: add PMD for AF_PACKET-based virtual devices")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
>> ---
>> drivers/net/af_packet/rte_eth_af_packet.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c
>> index 397a32db58..28aeb7d08e 100644
>> --- a/drivers/net/af_packet/rte_eth_af_packet.c
>> +++ b/drivers/net/af_packet/rte_eth_af_packet.c
>> @@ -6,6 +6,7 @@
>> * All rights reserved.
>> */
>>
>> +#include <rte_common.h>
>> #include <rte_string_fns.h>
>> #include <rte_mbuf.h>
>> #include <ethdev_driver.h>
>> @@ -53,7 +54,7 @@ struct pkt_rx_queue {
>>
>> volatile unsigned long rx_pkts;
>> volatile unsigned long rx_bytes;
>> -};
>> +} __rte_cache_aligned;
>>
>> struct pkt_tx_queue {
>> int sockfd;
>> @@ -67,7 +68,7 @@ struct pkt_tx_queue {
>> volatile unsigned long tx_pkts;
>> volatile unsigned long err_pkts;
>> volatile unsigned long tx_bytes;
>> -};
>> +} __rte_cache_aligned;
>>
>> struct pmd_internals {
>> unsigned nb_queues;
>
> Hi Mattias,
>
> I guess my comment missed, location of '__rte_cache_aligned' tag changed
> for MSVC support, it should be like:
> ```
> struct __rte_cache_aligned pkt_rx_queue {
> ...
> };
> ```
Right. Sorry, forgot about that.
I've made a v3 (which is actually marked v3).
@@ -6,6 +6,7 @@
* All rights reserved.
*/
+#include <rte_common.h>
#include <rte_string_fns.h>
#include <rte_mbuf.h>
#include <ethdev_driver.h>
@@ -53,7 +54,7 @@ struct pkt_rx_queue {
volatile unsigned long rx_pkts;
volatile unsigned long rx_bytes;
-};
+} __rte_cache_aligned;
struct pkt_tx_queue {
int sockfd;
@@ -67,7 +68,7 @@ struct pkt_tx_queue {
volatile unsigned long tx_pkts;
volatile unsigned long err_pkts;
volatile unsigned long tx_bytes;
-};
+} __rte_cache_aligned;
struct pmd_internals {
unsigned nb_queues;