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diff --git a/Documentation/misc-devices/mic/scif_overview.rst b/Documentation/misc-devices/mic/scif_overview.rst deleted file mode 100644 index 4c8ad9e43706..000000000000 --- a/Documentation/misc-devices/mic/scif_overview.rst +++ /dev/null @@ -1,108 +0,0 @@ -======================================== -Symmetric Communication Interface (SCIF) -======================================== - -The Symmetric Communication Interface (SCIF (pronounced as skiff)) is a low -level communications API across PCIe currently implemented for MIC. Currently -SCIF provides inter-node communication within a single host platform, where a -node is a MIC Coprocessor or Xeon based host. SCIF abstracts the details of -communicating over the PCIe bus while providing an API that is symmetric -across all the nodes in the PCIe network. An important design objective for SCIF -is to deliver the maximum possible performance given the communication -abilities of the hardware. SCIF has been used to implement an offload compiler -runtime and OFED support for MPI implementations for MIC coprocessors. - -SCIF API Components -=================== - -The SCIF API has the following parts: - -1. Connection establishment using a client server model -2. Byte stream messaging intended for short messages -3. Node enumeration to determine online nodes -4. Poll semantics for detection of incoming connections and messages -5. Memory registration to pin down pages -6. Remote memory mapping for low latency CPU accesses via mmap -7. Remote DMA (RDMA) for high bandwidth DMA transfers -8. Fence APIs for RDMA synchronization - -SCIF exposes the notion of a connection which can be used by peer processes on -nodes in a SCIF PCIe "network" to share memory "windows" and to communicate. A -process in a SCIF node initiates a SCIF connection to a peer process on a -different node via a SCIF "endpoint". SCIF endpoints support messaging APIs -which are similar to connection oriented socket APIs. Connected SCIF endpoints -can also register local memory which is followed by data transfer using either -DMA, CPU copies or remote memory mapping via mmap. SCIF supports both user and -kernel mode clients which are functionally equivalent. - -SCIF Performance for MIC -======================== - -DMA bandwidth comparison between the TCP (over ethernet over PCIe) stack versus -SCIF shows the performance advantages of SCIF for HPC applications and -runtimes:: - - Comparison of TCP and SCIF based BW - - Throughput (GB/sec) - 8 + PCIe Bandwidth ****** - + TCP ###### - 7 + ************************************** SCIF %%%%%% - | %%%%%%%%%%%%%%%%%%% - 6 + %%%% - | %% - | %%% - 5 + %% - | %% - 4 + %% - | %% - 3 + %% - | % - 2 + %% - | %% - | % - 1 + - + ###################################### - 0 +++---+++--+--+-+--+--+-++-+--+-++-+--+-++-+- - 1 10 100 1000 10000 100000 - Transfer Size (KBytes) - -SCIF allows memory sharing via mmap(..) between processes on different PCIe -nodes and thus provides bare-metal PCIe latency. The round trip SCIF mmap -latency from the host to an x100 MIC for an 8 byte message is 0.44 usecs. - -SCIF has a user space library which is a thin IOCTL wrapper providing a user -space API similar to the kernel API in scif.h. The SCIF user space library -is distributed @ https://software.intel.com/en-us/mic-developer - -Here is some pseudo code for an example of how two applications on two PCIe -nodes would typically use the SCIF API:: - - Process A (on node A) Process B (on node B) - - /* get online node information */ - scif_get_node_ids(..) scif_get_node_ids(..) - scif_open(..) scif_open(..) - scif_bind(..) scif_bind(..) - scif_listen(..) - scif_accept(..) scif_connect(..) - /* SCIF connection established */ - - /* Send and receive short messages */ - scif_send(..)/scif_recv(..) scif_send(..)/scif_recv(..) - - /* Register memory */ - scif_register(..) scif_register(..) - - /* RDMA */ - scif_readfrom(..)/scif_writeto(..) scif_readfrom(..)/scif_writeto(..) - - /* Fence DMAs */ - scif_fence_signal(..) scif_fence_signal(..) - - mmap(..) mmap(..) - - /* Access remote registered memory */ - - /* Close the endpoints */ - scif_close(..) scif_close(..) |