Product specifications
Table Of Contents
- Table of Contents
- 1 Introduction
- 2 Feature Overview
- 3 Step-by-Step Cluster Setup and MPI Usage Checklists
- 4 InfiniPath Cluster Setup and Administration
- Introduction
- Installed Layout
- Memory Footprint
- BIOS Settings
- InfiniPath and OpenFabrics Driver Overview
- OpenFabrics Drivers and Services Configuration and Startup
- Other Configuration: Changing the MTU Size
- Managing the InfiniPath Driver
- More Information on Configuring and Loading Drivers
- Performance Settings and Management Tips
- Host Environment Setup for MPI
- Checking Cluster and Software Status
- 5 Using QLogic MPI
- Introduction
- Getting Started with MPI
- QLogic MPI Details
- Use Wrapper Scripts for Compiling and Linking
- Configuring MPI Programs for QLogic MPI
- To Use Another Compiler
- Process Allocation
- mpihosts File Details
- Using mpirun
- Console I/O in MPI Programs
- Environment for Node Programs
- Environment Variables
- Running Multiple Versions of InfiniPath or MPI
- Job Blocking in Case of Temporary InfiniBand Link Failures
- Performance Tuning
- MPD
- QLogic MPI and Hybrid MPI/OpenMP Applications
- Debugging MPI Programs
- QLogic MPI Limitations
- 6 Using Other MPIs
- A mpirun Options Summary
- B Benchmark Programs
- C Integration with a Batch Queuing System
- D Troubleshooting
- Using LEDs to Check the State of the Adapter
- BIOS Settings
- Kernel and Initialization Issues
- OpenFabrics and InfiniPath Issues
- Stop OpenSM Before Stopping/Restarting InfiniPath
- Manual Shutdown or Restart May Hang if NFS in Use
- Load and Configure IPoIB Before Loading SDP
- Set $IBPATH for OpenFabrics Scripts
- ifconfig Does Not Display Hardware Address Properly on RHEL4
- SDP Module Not Loading
- ibsrpdm Command Hangs when Two Host Channel Adapters are Installed but Only Unit 1 is Connected to the Switch
- Outdated ipath_ether Configuration Setup Generates Error
- System Administration Troubleshooting
- Performance Issues
- QLogic MPI Troubleshooting
- Mixed Releases of MPI RPMs
- Missing mpirun Executable
- Resolving Hostname with Multi-Homed Head Node
- Cross-Compilation Issues
- Compiler/Linker Mismatch
- Compiler Cannot Find Include, Module, or Library Files
- Problem with Shell Special Characters and Wrapper Scripts
- Run Time Errors with Different MPI Implementations
- Process Limitation with ssh
- Number of Processes Exceeds ulimit for Number of Open Files
- Using MPI.mod Files
- Extending MPI Modules
- Lock Enough Memory on Nodes When Using a Batch Queuing System
- Error Creating Shared Memory Object
- gdb Gets SIG32 Signal Under mpirun -debug with the PSM Receive Progress Thread Enabled
- General Error Messages
- Error Messages Generated by mpirun
- MPI Stats
- E Write Combining
- F Useful Programs and Files
- G Recommended Reading
- Glossary
- Index
D–Troubleshooting
System Administration Troubleshooting
IB6054601-00 H D-9
A
System Administration Troubleshooting
The following sections provide details on locating problems related to system
administration.
Broken Intermediate Link
Sometimes message traffic passes through the fabric while other traffic appears
to be blocked. In this case, MPI jobs fail to run.
In large cluster configurations, switches may be attached to other switches to
supply the necessary inter-node connectivity. Problems with these inter-switch (or
intermediate) links are sometimes more difficult to diagnose than failure of the
final link between a switch and a node. The failure of an intermediate link may
allow some traffic to pass through the fabric while other traffic is blocked or
degraded.
If you notice this behavior in a multi-layer fabric, check that all switch cable
connections are correct. Statistics for managed switches are available on a
per-port basis, and may help with debugging. See your switch vendor for more
information.
Two diagnostic tools, ibhosts and ibtracert, may also be helpful. The tool
ibhosts lists all the InfiniBand nodes that the subnet manager recognizes. To
check the InfiniBand path between two nodes, use the ibtracert command.
Performance Issues
The following sections discuss known performance issues.
Unexpected Low Bandwidth or Poor Latency
If MTRR mapping is used for write combining (instead of the PAT mechanism), the
BIOS must be set to Discrete if there is 4GB or more memory in the system; it
affects where the PCI, PCIe, and HyperTransport I/O Base Address Registers
(BARs) are mapped. If there is 4GB or more memory in the system, and the
MTRR mapping is not set to Discrete, the bandwidth will be very low (under
250 MBps) on anything that normally runs near full bandwidth over the QHT7140
and QLE7140 adapters.
Since QLE7240 and QLE7280 adapters use SendDMA rather than PIO for larger
messages, peak message bandwidth is no longer a symptom of this problem. In
this case, it appears as poor latency with small (less than 8K) messages.