docs: clarify vector element alignment description.

Change-Id: I6da153779010263e6fc4b51c64b01444aaadca17
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>

2 files changed, 16 insertions, 11 deletions

diff --git a/docs/gettingstarted/developers/infrastructure.md b/docs/gettingstarted/developers/infrastructure.md
index 0361a632c37..b99460732c5 100644
--- a/docs/gettingstarted/developers/infrastructure.md
+++ b/docs/gettingstarted/developers/infrastructure.md
@@ -48,13 +48,16 @@ macro! It's smart about NULL pointers.\]
 
 Typically, the user header is not present. User headers allow for other
 data structures to be built atop vppinfra vectors. Users may specify the
-alignment for data elements via the [vec]()\*\_aligned macros.
+alignment for first data element of a vector via the [vec]()\*\_aligned
+macros. 
 
-Vectors elements can be any C type e.g. (int, double, struct bar). This
+Vector elements can be any C type e.g. (int, double, struct bar). This
 is also true for data types built atop vectors (e.g. heap, pool, etc.).
-Many macros have \_a variants supporting alignment of vector data and
-\_h variants supporting non-zero-length vector headers. The \_ha
-variants support both.
+Many macros have \_a variants supporting alignment of vector elements
+and \_h variants supporting non-zero-length vector headers. The \_ha
+variants support both.  Additionally cacheline alignment within a
+vector element structure can be specified using the
+[CLIB_CACHE_LINE_ALIGN_MARK]() macro.
 
 Inconsistent usage of header and/or alignment related macro variants
 will cause delayed, confusing failures.
diff --git a/src/vppinfra/vec.h b/src/vppinfra/vec.h
index 470a4f190c2..6f0e7e9148b 100644
--- a/src/vppinfra/vec.h
+++ b/src/vppinfra/vec.h
@@ -70,16 +70,18 @@
    Typically, the header is not present.  Headers allow for other
    data structures to be built atop CLIB vectors.
 
-   Users may specify the alignment for data elements via the
-   vec_*_aligned macros.
+   Users may specify the alignment for first data element of a vector
+   via the vec_*_aligned macros.
 
-   Vectors elements can be any C type e.g. (int, double, struct bar).
+   Vector elements can be any C type e.g. (int, double, struct bar).
    This is also true for data types built atop vectors (e.g. heap,
    pool, etc.).
 
-   Many macros have _a variants supporting alignment of vector data
-   and _h variants supporting non zero length vector headers.
-   The _ha variants support both.
+   Many macros have \_a variants supporting alignment of vector elements
+   and \_h variants supporting non-zero-length vector headers. The \_ha
+   variants support both.  Additionally cacheline alignment within a
+   vector element structure can be specified using the
+   CLIB_CACHE_LINE_ALIGN_MARK() macro.
 
    Standard programming error: memorize a pointer to the ith element
    of a vector then expand it. Vectors expand by 3/2, so such code