UCP/PROTOV1: Remove redundant fieds from request structure

[ivankochin]

What

Removes redundant fields from request structure.

Why ?

To avoid increasing ucp_request structure size after merging #9814

Notes

Performance was tested on osu_latency, osu_bw and osu_mbw_mr benchmarks

[yosefe]

popcount is not converted to CPU instruction when not passing --enable-optimizations flag
so we should avoid it in fast path
maybe we can keep it in the request, it's not so big anyway

[ivankochin]

union {
    struct {
        /* Actual lanes map */
        ucp_lane_map_t lanes_map_all;

        /* Actual lanes count */
        uint8_t        lanes_count;
    } zcopy;

    struct {
        /* Data start offset of this request */
        size_t offset;
    } rtr;
};

That is the part of ucp_request where lanes_count is stored. If size of ucp_lane_map_t is less than 8, everything is OK since lanes_count + lanes_map_all fields took no more than offset, so union has 8 bytes size.

But if ucp_lane_map_t has 8 bytes, lanes_count became the 9th byte, so the union size became 16 bytes .

The only possible option that I see is to move that 1-byte field to another place inside ucp_request sturcture, but all other fields inside struct rndv {...} have 8-byte size, so on any place it would create 7 byte padding.

Is that so significant to have that value prestored in that field instead of popcount on that place? I mean that RMA flow which is often used for big messages and that's only for protov1, WDYT?

[yosefe]

ok, though maybe worth converting ucs_assert_always(lanes_count > 0); to ucs_assert(ucs_popcount(lanes_count) > 0); and remove the local var lanes_count, so it will be calculated only when needed in release mode

[ivankochin]

Done.

[brminich]

why not changed to assert?

[ivankochin]

Good catch, removed!