NCCL通信协议一共有Simple, LL, LL128,本篇博客只关注后两种通信协议。 L(ow)L(atency)协议 以往NCCL为了保证同步,会引入 memory fence,这就导致延迟比较大。 而在小数据量下,往往打不满传输带宽,此时优化点在于同步带来的延迟。 LL协议依赖前提是 CUDA 的memory 8Bytes大小的操作是atomic的,因此通信时会将数...
协议:数据构建的协议影响速度,可选的protocol主要是三种,低延时/128B低延时/常规 对应参数:LL/LL128/'Simple。 算法带宽的计算过程:取算法基数值 busBw= ncclTopoGraph->bwIntra ,经过NCCL_ALGO/NCCL_PROTO/NCCL_TOPO等场景修正(即乘以一定的比例系数)后,把结果存储在comm中: 参数含义:coll: 集群通信操作;a:...
The NCCL_PROTO variable defines which protocol(s) NCCL will be allowed to use. Users are discouraged from setting this variable, with the exception of disabling a specific protocol in case a bug in NCCL is suspected. In particular, enabling LL128 on platforms that don’t support it can lead...
TheNCCL_PROTOvariable defines which protocol NCCL will use. Values accepted¶ Coma-separated list of protocols (not case sensitive) among: LL, LL128, Simple. To specify protocols to exclude (instead of include), start the list with ^. ...
[0] NCCL INFO Protocol | LL | LL128 | Simple | LL | LL128 | Simple | LL | LL128 | Simple | nathan-h100-1:14492:14605 [0] NCCL INFO Max NThreads | 0 | 0 | 640 | 0 | 0 | 640 | 0 | 0 | 640 | nathan-h100-1:14492:14605 [0] NCCL INFO Broadcast | 0.0/ 0.0 | 0.0...
axon:5019:5088 [0] NCCL INFO Protocol | LL | LL128 | Simple | LL | LL128 | Simple | LL | LL128 | Simple | axon:5019:5088 [0] NCCL INFO Max NThreads | 0 | 0 | 640 | 0 | 0 | 640 | 0 | 0 | 640 | axon:5019:5088 [0] NCCL INFO Broadcast | 0.0/ 0.0 | 0.0/ 0.0...
static ncclResult_t computeColl(struct ncclInfo* info /* input */, struct ncclColl* coll, struct ncclProxyArgs* proxyArgs /* output */) {...int stepSize = info->comm->buffSizes[info->protocol]/NCCL_STEPS;int chunkSteps = (info->protocol == NCCL_PROTO_SIMPLE && info->algorithm ==...
The overhead bytes are protocol overhead for using nvlink, and not specific to nccl. It’s hard to say why the ratio is what it is. Perhaps the algorithm is only sending small amounts of data per transmission. You may need to talk with the nccl team or dig deeper into the perf ana...
The overhead bytes are protocol overhead for using nvlink, and not specific to nccl. It’s hard to say why the ratio is what it is. Perhaps the algorithm is only sending small amounts of data per transmission. You may need to talk with the nccl team or dig deeper into the perf ana...
It responds to the GET * method of the HTTP protocol. */ @DeclareRoles("helloUser") public class GreetingServlet extends HttpServlet { public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException...