Hello all,
While going through the VPP code, I have not fully understood what
the following functions mean and when should they be used?
1. static_always_inline void
vlib_buffer_enqueue_to_next (vlib_main_t * vm, vlib_node_runtime_t * node,
u32 * buffers, u16 * nexts, uword count)
I could see following comments about this function
/*
* Send the packets along their respective next-node graph arcs
* Considerable locality of reference is expected, most if not all
* packets in the inbound vector will traverse the same next-node
* arc
*/
I tried reading through the code but could not figure out what this
function does, and how this is implemented. I see that the code has
optimizations for various CPU, but not could not figure out what those
optimizations are.
2. #define vlib_prefetch_buffer_header (b, type )
CLIB_PREFETCH (b, 64, type)
This gets expanded to:
#define _CLIB_PREFETCH(n,size,type) \
if ((size) > (n)*CLIB_CACHE_LINE_BYTES) \
__builtin_prefetch (_addr + (n)*CLIB_CACHE_LINE_BYTES, \
CLIB_PREFETCH_##type, \
/* locality */ 3);
type can be either LOAD or STORE. What is the purpose of these two operations?
I am sure I am missing some thing with respect to understanding
prefetch. I assume LOAD will prefetch data from memory, and STORE
performs its inverse operation?
Thanks and Regards,
Raj
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