QLogic OFED+ Host Software User Guide, Rev. B

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7–Dispersive Routing Internally, PSM utilizes dispersive routing differently for small and large messages. Large messages are any messages greater-than or equal-to 64K. For large messages, the message is split into message fragments of 128K by default (called a window). Each of these message windows is sprayed across a distinct path between ports. All packets belonging to a window utilize the same path however the windows themselves can take a different path through the fabric. PSM assembles the windows that make up an MPI message before delivering it to the application. This allows limited out of order semantics through the fabrics to be maintain with little overhead. Small messages on the other hand always utilize a single path when communicating to a remote node however different processes executing on a node can utilize different paths for their communication between the nodes. For example, two nodes A and B each with 8 processors per node. Assuming the fabric is configured for a LMC of 3, PSM constructs 8 paths through the fabric as described above and a 16 process MPI application that spans these nodes (8 process per node). Then: • Each MPI process is automatically bound to a given CPU core numbered between 0-7. PSM does this at startup to get improved cache hit rates and other benefits. • Small Messages sent from a process on core N will use path N. NOTE: Only path N will be used by this process for all communications to any process on the remote node. • For a large message, each process will utilize all of the 8 paths and spray the windowed messages across it. The above highlights the default path selection policy that is active in PSM when running on non-zero LMC configured fabrics. There are 3 other path selection policies that determine how to select the path (or path index from the set of available paths) used by a process when communicating with a remote node. The above path policy is called adaptive. The 3 remaining path policies are static policies that assign a static path on job startup for both small and large message transfers. • Static_Src: Only one path per process is used for all remote communications. The path index is based on the CPU number the process is running. NOTE: Multiple paths are still used in the fabric if multiple processes (each on a different CPU) are communicating. 7-2 D000046-005 B
7–Dispersive Routing • Static_Dest: The path selection is based on the CPU index of the destination process. Multiple paths can be used if data transfer is to different remote processes within a node. If multiple processes from Node A send a message to a single process on Node B only one path will be used across all processes. • Static_Base: The only path that is used is the base path [SLID,DLID] between nodes regardless of the LMC of the fabric or the number of paths available. This is similar to how PSM operated till the IFS 5.1 release. NOTE: A fabric configured with LMC of 0 even with the default adaptive policy enabled operates as the Static_Base policy as there only exists a single path between any pairs of port. D000046-005 B 7-3
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QLogic OFED+ Host Software User Gui
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Table of Contents 1 Introduction Ho
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Preface The QLogic OFED+ Host Softw
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Preface Technical Support Technical
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1 Introduction How this Guide is Or
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1-Introduction Interoperability QLo
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2 Step-by-Step Cluster Setup and MP
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3 TrueScale Cluster Setup and Admin
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3-TrueScale Cluster Setup and Admin
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Page 61 and 62: 3-TrueScale Cluster Setup and Admin
Page 63 and 64: 4 Running QLogic MPI on QLogic Adap
Page 65 and 66: 4-Running QLogic MPI on QLogic Adap
Page 91 and 92: 5 Using Other MPIs Introduction Thi
Page 93 and 94: 5-Using Other MPIs Open MPI Open MP
Page 95 and 96: 5-Using Other MPIs MVAPICH Further
Page 97 and 98: 5-Using Other MPIs Managing Open MP
Page 99 and 100: 5-Using Other MPIs Platform (Scali)
Page 101 and 102: 5-Using Other MPIs Intel MPI Intel
Page 103 and 104: 5-Using Other MPIs Intel MPI When u
Page 105 and 106: 5-Using Other MPIs Improving Perfor
Page 107 and 108: 6 Performance Scaled Messaging Intr
Page 109 and 110: 6-Performance Scaled Messaging Usin
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Page 115 and 116: 8 gPXE gPXE Setup gPXE is an open s
Page 117 and 118: 8-gPXE Preparing the DHCP Server in
Page 119 and 120: 8-gPXE Netbooting Over InfiniBand P
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Page 129 and 130: 8-gPXE HTTP Boot Setup 5. Create an
Page 131 and 132: A mpirun Options Summary This secti
Page 133 and 134: A-mpirun Options Summary Quiescence
Page 135 and 136: A-mpirun Options Summary Tuning Opt
Page 137 and 138: A-mpirun Options Summary Format Opt
Page 139 and 140: B Benchmark Programs Several MPI pe
Page 141 and 142: B-Benchmark Programs Benchmark 2: M
Page 143 and 144: B-Benchmark Programs Benchmark 4: M
Page 145 and 146: C VirtualNIC Interface Configuratio
Page 147 and 148: C-VirtualNIC Interface Configuratio
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D-SRP Configuration QLogic SRP Conf
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D-SRP Configuration OFED SRP Config
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E Integration with a Batch Queuing
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E-Integration with a Batch Queuing
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E-Integration with a Batch Queuing
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F Troubleshooting This appendix des
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F-Troubleshooting Kernel and Initia
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F-Troubleshooting Kernel and Initia
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F-Troubleshooting OpenFabrics and I
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F-Troubleshooting Performance Issue
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F-Troubleshooting QLogic MPI Troubl
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G ULP Troubleshooting Troubleshooti
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G-ULP Troubleshooting Troubleshooti
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H Write Combining Introduction Writ
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H-Write Combining MTRR Mapping and
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I Useful Programs and Files The mos
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I-Useful Programs and Files Summary
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I-Useful Programs and Files Common
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J Recommended Reading Reference mat
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Corporate Headquarters QLogic Corpo
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