请问vccl中开启sm free可以在一个group内混合使用p2p通信和集合通信吗

[xueyunyong]

[leoda1]

@xueyunyong hi, P2P communication and Collective communication can be used together within a group.

[leoda1]

And you can take a look at the code if (connector->proxyConn.proxyProgress == NULL) return ncclSuccess; in the src/proxy.cc in SaveProxy function. Only the psm_p2p and psm_net transport tasks will to add proxyOpCnt, so it can corretcly sub to 0 by proxyProgress.

[xueyunyong]

And you can take a look at the code if (connector->proxyConn.proxyProgress == NULL) return ncclSuccess; in the src/proxy.cc in SaveProxy function. Only the psm_p2p and psm_net transport tasks will to add proxyOpCnt, so it can corretcly sub to 0 by proxyProgress.

@leoda1 Thank you for your response. Regarding the mixed use of coll and p2p in a group, by checking the code of ncclLaunchPrepare, scheduleCollTasksToPlan, and scheduleP2pTasksToPlan, it is possible for a plan to have both coll and p2p. In this case, the plan will share a kernel (plan->kernelFn). However, in the ncclLaunchKernel interface, the judgment is made using if (ncclParamPassSm() && plan->kernelFn == ncclDevKernelForFunc[ncclDevFuncId_P2p()]), which seems to assume that a plan only has one communication method. Maybe it can be modified like this. I'm not sure if my analysis is correct. Looking forward to your reply.

[leoda1]

@xueyunyong, p2p and coll can be placed in the same group, but they cannot be scheduled at the same time because nccl will schedule coll communication first by default.

[xueyunyong]

@xueyunyong, p2p and coll can be placed in the same group, but they cannot be scheduled at the same time because nccl will schedule coll communication first by default.
@leoda1 I know that coll should be scheduled first. However, after coll is scheduled, p2p will be called next, which means there is a possibility that coll and p2p will be in the same plan. The key issue is how to handle this plan. In the code, this plan is directly processed by a kernel, while in VCCL, it is handled by ncclLaunchKernel with the condition (ncclParamPassSm() && plan->kernelFn == ncclDevKernelForFunc[ncclDevFuncId_P2p()]). This condition cannot handle this plan.