[Question] Calculating GPUSet scores in allocation

[kerthcet]

From

go-gpuallocator/gpuallocator/device.go

Lines 117 to 131 in 8fc3087

	p2plink, err := links.GetP2PLink(d1, d2)
	if err != nil {
	return nil, fmt.Errorf("error getting P2PLink for devices (%v, %v): %v", i, j, err)
	}
	if p2plink != links.P2PLinkUnknown {
	d1.Links[d2.Index] = append(d1.Links[d2.Index], P2PLink{d2, p2plink})
	}
	nvlink, err := links.GetNVLink(d1, d2)
	if err != nil {
	return nil, fmt.Errorf("error getting NVLink for devices (%v, %v): %v", i, j, err)
	}
	if nvlink != links.P2PLinkUnknown {
	d1.Links[d2.Index] = append(d1.Links[d2.Index], P2PLink{d2, nvlink})
	}

What I learned is even two GPUs are connected via nvlink, we still need to get the P2PLink and accumulate the scores in allocation:

go-gpuallocator/gpuallocator/besteffort_policy.go

Lines 316 to 369 in 8fc3087

	for _, link := range gpu0.Links[gpu1.Index] {
	switch link.Type {
	case nvml.P2PLinkCrossCPU:
	score += 10
	case nvml.P2PLinkSameCPU:
	score += 20
	case nvml.P2PLinkHostBridge:
	score += 30
	case nvml.P2PLinkMultiSwitch:
	score += 40
	case nvml.P2PLinkSingleSwitch:
	score += 50
	case nvml.P2PLinkSameBoard:
	score += 60
	case nvml.SingleNVLINKLink:
	score += 100
	case nvml.TwoNVLINKLinks:
	score += 200
	case nvml.ThreeNVLINKLinks:
	score += 300
	case nvml.FourNVLINKLinks:
	score += 400
	case nvml.FiveNVLINKLinks:
	score += 500
	case nvml.SixNVLINKLinks:
	score += 600
	case nvml.SevenNVLINKLinks:
	score += 700
	case nvml.EightNVLINKLinks:
	score += 800
	case nvml.NineNVLINKLinks:
	score += 900
	case nvml.TenNVLINKLinks:
	score += 1000
	case nvml.ElevenNVLINKLinks:
	score += 1100
	case nvml.TwelveNVLINKLinks:
	score += 1200
	case nvml.ThirteenNVLINKLinks:
	score += 1300
	case nvml.FourteenNVLINKLinks:
	score += 1400
	case nvml.FifteenNVLINKLinks:
	score += 1500
	case nvml.SixteenNVLINKLinks:
	score += 1600
	case nvml.SeventeenNVLINKLinks:
	score += 1700
	case nvml.EighteenNVLINKLinks:
	score += 1800
	}
	}
	return score

What's the reason here? Doesn't these two GPUs are communicating through nvlink? Appreciate for the explanations.

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