>> Swapped position of mbuf next pointer and second dynamic field (dynfield2)
>> if the build is configured to use IOVA as VA. This is to move the mbuf
>> next pointer to first cache line. kni library is disabled for this
>> change as it depends on the offset value of next pointer.
>>
>> Signed-off-by: Shijith Thotton <sthot...@marvell.com>
>> ---
>> lib/mbuf/rte_mbuf_core.h | 29 +++++++++++++++++++++--------
>> lib/meson.build | 3 +++
>> 2 files changed, 24 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
>> index 94907f301d..915dcd8653 100644
>> --- a/lib/mbuf/rte_mbuf_core.h
>> +++ b/lib/mbuf/rte_mbuf_core.h
>> @@ -590,11 +590,14 @@ struct rte_mbuf {
>> * working on vector drivers easier.
>> */
>> rte_iova_t buf_iova __rte_aligned(sizeof(rte_iova_t));
>> +#if RTE_IOVA_AS_VA
>> /**
>> - * Reserved for dynamic field in builds where physical address
>> - * field is invalid.
>> + * Next segment of scattered packet.
>> + * This field is valid when physical address field is invalid.
>> + * Otherwise next pointer in the second cache line will be used.
>> */
>> - uint64_t dynfield2;
>> + struct rte_mbuf *next;
>> +#endif
>> };
>>
>> /* next 8 bytes are initialised on RX descriptor rearm */
>> @@ -711,11 +714,21 @@ struct rte_mbuf {
>> /* second cache line - fields only used in slow path or on TX */
>> RTE_MARKER cacheline1 __rte_cache_min_aligned;
>>
>> - /**
>> - * Next segment of scattered packet. Must be NULL in the last segment or
>> - * in case of non-segmented packet.
>> - */
>> - struct rte_mbuf *next;
>> + RTE_STD_C11
>> + union {
>> +#if !RTE_IOVA_AS_VA
>> + /**
>> + * Next segment of scattered packet. Must be NULL in the last
>> + * segment or in case of non-segmented packet.
>> + */
>> + struct rte_mbuf *next;
>> +#endif
>> + /**
>> + * Reserved for dynamic field when the next pointer is in first
>> + * cache line (i.e. RTE_IOVA_AS_VA is 1).
>> + */
>> + uint64_t dynfield2;
>> + };
>
>Same comment than other patches about union vs #if.
Okay. Will change.
>
>>
>> /* fields to support TX offloads */
>> RTE_STD_C11
>> diff --git a/lib/meson.build b/lib/meson.build
>> index c648f7d800..73d93bc803 100644
>> --- a/lib/meson.build
>> +++ b/lib/meson.build
>> @@ -88,6 +88,9 @@ optional_libs = [
>> disabled_libs = []
>> opt_disabled_libs = run_command(list_dir_globs, get_option('disable_libs'),
>> check: true).stdout().split()
>> +if dpdk_conf.get('RTE_IOVA_AS_VA') == 1
>> + opt_disabled_libs += ['kni']
>> +endif
>
>I guess this should be in the previous patch instead, since kni uses
>m->buf_iova
>
Ack.
>> foreach l:opt_disabled_libs
>> if not optional_libs.contains(l)
>> warning('Cannot disable mandatory library "@0@"'.format(l))
>
>
>After this change, the documentation of RTE_IOVA_AS_VA can be enhanced to
>explain that it also moves the next pointer to the first cache line, possibly
>increasing the performance.
Okay.
