On 4/23/2024 10:08 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
> makes no change there, but it does on 32-bit ISAs.
>
> TX struct is 56 bytes on x86_64.
>
Hi Mattias,
No objection to the patch. Is the improvement theoretical or do you
measure any improvement practically, if so how much is the improvement?
> Both structs keep counters, and in the RX case they are updated even
> for empty polls.
>
Do you think does it help if move 'rx_pkts' & 'rx_bytes' update within
the loop?
> Signed-off-by: Mattias Rönnblom <mattias.ronnb...@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;
>
Latest location for '__rte_cache_aligned' tag is at the beginning of the
struct [1], so something like:
`struct __rte_cache_aligned pkt_rx_queue {`
[1]
https://patchwork.dpdk.org/project/dpdk/list/?series=31746&state=%2A&archive=both
