[Perf] Two-node allreduce perf improvement

[Binyang2014]

Target:

n_ctx	size	custom (us)
1	24.0KiB	15.6
2	48.0KiB	16.6
3	72.0KiB	21.7
4	96.0KiB	17.8
8	192.0KiB	19.3
16	384.0KiB	22.7
24	576.0KiB	31.4
32	768.0KiB	28.3
48	1.1MiB	33.4
64	1.5MiB	38.4
128	3.0MiB	52.3
512	12.0MiB	139.7
1024	24.0MiB	252.7
2048	48.0MiB	476.8
4096	96.0MiB	930.2
8192	192.0MiB	1841.5

[Binyang2014]

Temp update

Size (fp16)	Time (us)	AlgBW (GB/s)	Correctness	NCCL Time (us)	NCCL AlgBW (GB/s)	NCCL Correctness	Speed Up
6.0 KiB	18.87	0.33	PASS	49.16	0.12	PASS	2.60
12.0 KiB	18.15	0.68	PASS	47.97	0.26	PASS	2.64
24.0 KiB	20.36	1.21	PASS	55.81	0.44	PASS	2.74
48.0 KiB	21.10	2.33	PASS	59.42	0.83	PASS	2.82
96.0 KiB	23.34	4.21	PASS	92.96	1.06	PASS	3.98
192.0 KiB	26.47	7.43	PASS	74.67	2.63	PASS	2.82
384.0 KiB	34.14	11.52	PASS	88.80	4.43	PASS	2.60
768.0 KiB	46.04	17.08	PASS	97.53	8.06	PASS	2.12
1.5 MiB	71.91	21.87	PASS	121.84	12.91	PASS	1.69
3.0 MiB	126.60	24.85	PASS	168.87	18.63	PASS	1.33
6.0 MiB	169.38	37.14	PASS	204.70	30.74	PASS	1.21
12.0 MiB	215.83	58.30	PASS	310.11	40.58	PASS	1.44
24.0 MiB	326.40	77.10	PASS	516.83	48.69	PASS	1.58
48.0 MiB	522.58	96.31	PASS	762.47	66.01	PASS	1.46
96.0 MiB	927.87	108.49	PASS	1324.39	76.01	PASS	1.43
192.0 MiB	1728.29	116.49	PASS	2312.49	87.06	PASS	1.34
384.0 MiB	3350.12	120.19	PASS	4352.33	92.51	PASS	1.30
768.0 MiB	6637.77	121.32	PASS	8448.14	95.32	PASS	1.27
1.5 GiB	12953.08	124.34	PASS	16360.09	98.45	PASS	1.26
3.0 GiB	25692.61	125.38	PASS	32297.60	99.74	PASS	1.26