Hi Jerrin,
>
> Hi All,
>
> I would like align mbuff rearm_data field to 8 byte aligned so that
> write to mbuf->rearm_data with uint64_t* will be naturally aligned.
> I am not sure about IA but some other architecture/implementation has overhead
> in non-naturally aligned stores.
>
> Proposed patch is something like this below, But open for any change to
> make fit for all other architectures/platform.
>
> Any thoughts ?
>
> ? [master] [dpdk-master] $ git diff
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 529debb..5a917d0 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -733,10 +733,8 @@ struct rte_mbuf {
> void *buf_addr; /**< Virtual address of segment
> buffer. */
> phys_addr_t buf_physaddr; /**< Physical address of segment
> buffer. */
>
> - uint16_t buf_len; /**< Length of segment buffer. */
> -
There is no need to move buf_len itself, I think.
Just move rearm_data marker prior to buf_len is enough.
Though how do you suggest to deal with the fact, that right now we blindly
update the whole 64bits pointed by rearm_data:
drivers/net/ixgbe/ixgbe_rxtx_vec.c:
/*
* Flush mbuf with pkt template.
* Data to be rearmed is 6 bytes long.
* Though, RX will overwrite ol_flags that are coming next
* anyway. So overwrite whole 8 bytes with one load:
* 6 bytes of rearm_data plus first 2 bytes of ol_flags.
*/
p0 = (uintptr_t)&mb0->rearm_data;
*(uint64_t *)p0 = rxq->mbuf_initializer;
?
If buf_len will be inside these 64bits, we can't do it anymore.
Are you suggesting something like:
uint64_t *p0, v0;
p0 = &mb0->rearm_data;
v0 = *p0 & REARM_MASK;
*p0 = v0 | rxq->mbuf_initializer;
?
If so I wonder what would be the performance impact of that change.
Konstantin
> /* next 6 bytes are initialised on RX descriptor rearm */
> - MARKER8 rearm_data;
> + MARKER64 rearm_data;
> uint16_t data_off;
>
> /**
> @@ -754,6 +752,7 @@ struct rte_mbuf {
> uint8_t nb_segs; /**< Number of segments. */
> uint8_t port; /**< Input port. */
>
> + uint16_t buf_len; /**< Length of segment buffer. */
> uint64_t ol_flags; /**< Offload features. */
>
> /* remaining bytes are set on RX when pulling packet from
> * descriptor
>
> /Jerin
