> From: Tyler Retzlaff [mailto:roret...@linux.microsoft.com] > Sent: Thursday, 21 March 2024 16.31 > > On Thu, Mar 21, 2024 at 10:32:02AM +0000, Bruce Richardson wrote: > > On Wed, Mar 20, 2024 at 03:01:36PM -0700, Tyler Retzlaff wrote: > > > RTE_MARKER typedefs are a GCC extension unsupported by MSVC. Remove > > > RTE_MARKER fields from rte_mbuf struct. > > > > > > Maintain alignment of fields after removed cacheline1 marker by placing > > > C11 alignas(RTE_CACHE_LINE_MIN_SIZE). > > > > > > Provide new rearm_data and rx_descriptor_fields1 fields in anonymous > > > unions as single element arrays of with types matching the original > > > markers to maintain API compatibility. > > > > > > Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com> > > > --- > > > doc/guides/rel_notes/release_24_03.rst | 2 + > > > lib/mbuf/rte_mbuf.h | 4 +- > > > lib/mbuf/rte_mbuf_core.h | 188 ++++++++++++++++++---------- > ----- > > > 3 files changed, 104 insertions(+), 90 deletions(-) > > > > > > diff --git a/doc/guides/rel_notes/release_24_03.rst > b/doc/guides/rel_notes/release_24_03.rst > > > index 14826ea..4f18cca 100644 > > > --- a/doc/guides/rel_notes/release_24_03.rst > > > +++ b/doc/guides/rel_notes/release_24_03.rst > > > @@ -216,6 +216,8 @@ Removed Items > > > > > > * acc101: Removed obsolete code for non productized HW variant. > > > > > > +* mbuf: ``RTE_MARKER`` fields ``cacheline0`` and ``cacheline1`` > > > + have been removed from ``struct rte_mbuf``. > > > > > > API Changes > > > ----------- > > > diff --git a/lib/mbuf/rte_mbuf.h b/lib/mbuf/rte_mbuf.h > > > index 286b32b..4c4722e 100644 > > > --- a/lib/mbuf/rte_mbuf.h > > > +++ b/lib/mbuf/rte_mbuf.h > > > @@ -108,7 +108,7 @@ > > > static inline void > > > rte_mbuf_prefetch_part1(struct rte_mbuf *m) > > > { > > > - rte_prefetch0(&m->cacheline0); > > > + rte_prefetch0(m); > > > } > > > > > > /** > > > @@ -126,7 +126,7 @@ > > > rte_mbuf_prefetch_part2(struct rte_mbuf *m) > > > { > > > #if RTE_CACHE_LINE_SIZE == 64 > > > - rte_prefetch0(&m->cacheline1); > > > + rte_prefetch0(RTE_PTR_ADD(m, RTE_CACHE_LINE_MIN_SIZE)); > > > #else > > > RTE_SET_USED(m); > > > #endif > > > diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h > > > index 9f58076..665213c 100644 > > > --- a/lib/mbuf/rte_mbuf_core.h > > > +++ b/lib/mbuf/rte_mbuf_core.h > > > @@ -465,8 +465,6 @@ enum { > > > * The generic rte_mbuf, containing a packet mbuf. > > > */ > > > struct __rte_cache_aligned rte_mbuf { > > > - RTE_MARKER cacheline0; > > > - > > > void *buf_addr; /**< Virtual address of segment buffer. */ > > > #if RTE_IOVA_IN_MBUF > > > /** > > > @@ -488,116 +486,130 @@ struct __rte_cache_aligned rte_mbuf { > > > #endif > > > > > > /* next 8 bytes are initialised on RX descriptor rearm */ > > > - RTE_MARKER64 rearm_data; > > > - uint16_t data_off; > > > - > > > - /** > > > - * Reference counter. Its size should at least equal to the size > > > - * of port field (16 bits), to support zero-copy broadcast. > > > - * It should only be accessed using the following functions: > > > - * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and > > > - * rte_mbuf_refcnt_set(). The functionality of these functions (atomic, > > > - * or non-atomic) is controlled by the RTE_MBUF_REFCNT_ATOMIC flag. > > > - */ > > > - RTE_ATOMIC(uint16_t) refcnt; > > > + union { > > > + uint64_t rearm_data[1]; > > > + __extension__ > > > + struct { > > > + uint16_t data_off; > > > + > > > + /** > > > + * Reference counter. Its size should at least equal to > the size > > > + * of port field (16 bits), to support zero-copy > broadcast. > > > + * It should only be accessed using the following > functions: > > > + * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and > > > + * rte_mbuf_refcnt_set(). The functionality of these > functions (atomic, > > > + * or non-atomic) is controlled by the > RTE_MBUF_REFCNT_ATOMIC flag. > > > + */ > > > + RTE_ATOMIC(uint16_t) refcnt; > > > > > > - /** > > > - * Number of segments. Only valid for the first segment of an mbuf > > > - * chain. > > > - */ > > > - uint16_t nb_segs; > > > + /** > > > + * Number of segments. Only valid for the first segment > > > of > an mbuf > > > + * chain. > > > + */ > > > + uint16_t nb_segs; > > > > > > - /** Input port (16 bits to support more than 256 virtual ports). > > > - * The event eth Tx adapter uses this field to specify the output port. > > > - */ > > > - uint16_t port; > > > + /** Input port (16 bits to support more than 256 virtual > ports). > > > + * The event eth Tx adapter uses this field to specify > > > the > output port. > > > + */ > > > + uint16_t port; > > > + }; > > > + }; > > > > > > uint64_t ol_flags; /**< Offload features. */ > > > > > > /* remaining bytes are set on RX when pulling packet from descriptor */ > > > - RTE_MARKER rx_descriptor_fields1; > > > - > > > - /* > > > - * The packet type, which is the combination of outer/inner L2, L3, L4 > > > - * and tunnel types. The packet_type is about data really present in the > > > - * mbuf. Example: if vlan stripping is enabled, a received vlan packet > > > - * would have RTE_PTYPE_L2_ETHER and not RTE_PTYPE_L2_VLAN because the > > > - * vlan is stripped from the data. > > > - */ > > > union { > > > - uint32_t packet_type; /**< L2/L3/L4 and tunnel information. */ > > > + void *rx_descriptor_fields1[1]; > > > > Can we make this array the actual size of all the fields, rather than just > > an 8-byte value? That would allow the right think to be done if assigning > > the descriptor fields from one mbuf to another, or when using memset or > > memcpy on them. > > Morten pointed out in a previous version that the marker being an array of > void * was a bug to begin with. > > The other field of the union is 24 bytes. I suppose it would be possible > to conditionally compile the array to be either 3 or 6 elements. I guess > this would be an improvement over what the marker is doing now.
Agree; it would be an improvement to give it the same size as the other struct in the union. > > Just a reminder that we cannot 'correct' the type since that would > require adaptation of calling code. I considered the following: Only drivers should be using rx_descriptor_fields1. We could probably change it to an array of uint64_t (or uint32_t, or even uint8_t) without breaking anything, because the drivers should only be using the address of rx_descriptor_fields1, not the value of it. However, keeping it an array of void* is certain to avoid any 32/64 bit CPU alignment related issues, because void* is the natural size to any CPU. > > What do others think? Keep it as a single element array or conditional > compile based on sizeof(void *)? Going for an array of 3/6 void pointers should be safe. I'm in favor of this. At your discretion, if you think it clarifies anything, consider adding a comment that the type void* is used for historical reasons (or something similar).
