[Contents] [Preface] [Chapter 2] [Index]
This chapter provides a description of Compaq PVM, and the information required to install it. The chapter consists of the following sections:
Compaq PVM is an implementation of the PVM message-passing system. The main advantage of Compaq PVM is that it uses shared memory and Memory Channel for PCI to provide low latency and high bandwidth communications.
Compaq PVM
is based on PVM Version 3.3.9, available from Oak Ridge National Laboratory, and is optimized for operation on AlphaServers and AlphaServer®
Memory Channel
clusters.
Memory Channel
is a high performance network for clusters of SMP AlphaServers running the
Compaq
Tru64™ UNIX
® (formerly DIGITAL® UNIX) operating system.
This release implements support for multiple Memory Channel rails.
This section describes the requirements to check before installing Compaq PVM: how to install the Compaq PVM kit; and, after installation, how to change configurations, initialize machines in a cluster, and add a host to the virtual machine.
You need the following hardware to run Compaq PVM:
You need the following software to run Compaq PVM:
Note: If you are using multiple Memory Channel rails, you must use Tru64 UNIX Version 4.0D and TruCluster Version 1.5.
To install Compaq PVM from a CD-ROM, follow these steps.
Read any release notes that come with the kit. (See the PSE Installation Guide for more information on installing Compaq PVM.)
Log in to the machine running the Tru64 UNIX operating system, as root.
To install the kit, enter the following commands, substituting your CD-ROM drive name for rzxxc:
The Compaq PVM installation comprises the following two subsets:
To verify Compaq PVM is installed correctly, enter the following command:
If you are using Memory Channel, you must check that each machine in the cluster is initialized for user-level access. For more information, refer to the Memory Channel User Guide.
To check and initialize, if necessary, follow these steps:
To search for the process imc_mapper on each machine, enter this command:
If the process described in step 1 does not exist on a machine you intend using as part of the cluster, enter the following command as root on the machine:
You enter this once and it is in effect until the machine is shut down.
To increase the total amount of Memory Channel address space available to the TruCluster Memory Channel Software and Compaq PVM, refer to the imc_init man page for details.
To increase the allocate and receive Memory Channel resources to 100 MB, enter:
Ensure that the /etc/sysconfigtab file contains the following entry:
This prevents Memory Channel resources from being inherited by a forked process.
If you are using multiple Memory Channel rails, the default setting is to use them as a failover pair. While this provides maximum availability, you can achieve increased performance by configuring your cluster to use the single-rail style. This allows applications to access the aggregate address space of all logical rails and utilize aggregate bandwidth.
To configure the use of the single-rail style, change the /etc/sysconfigtab file by adding or modifying the following entry:
Compaq PVM uses shared memory for communication within a host, and Memory Channel for communication between hosts. This is achieved by setting up "communication channels", each of which is either a shared memory segment or a group of Memory Channel pages. Shared memory is also used for each PVM task's "pack" buffer. The size of the shared memory "pack" buffer is controlled by the PVM_BUF_SIZE environment variable.
Performance characteristics can be changed by altering the size of the communication channels. The size of the shared memory communication channel is set by the PVM_SM_CHAN_SIZE environment variable. The size of the Memory Channel communication channel is set by the PVM_MC_CHAN_SIZE environment variable.
If very large applications are being run, it may be appropriate to increase the data and stack size using the limit command; for example,
To increase the maximum shared memory size, edit the /etc/sysconfigtab file and include or modify the following entry:
There are kernel limits on the number of shared memory segments a process can attach to and the total number of system-wide shared memory segments available.
To modify the value of the shm-seg variable, edit the /etc/sysconfigtab file and include or modify the following entry:
The total number of system-wide shared memory segments allowed is controlled by the shm-mni variable.
To change the system parameter, edit the /etc/sysconfigtab file and include or modify the following entry:
If you have changed any of the parameters as described in 1, 2 or 3 above, reboot the system.
Communication across Memory Channel uses a similar scheme to shared memory. The maximum Memory Channel allocation allowed is set by default to 10MB. There is a limit of 128MB on Memory Channel allocation using Memory Channel Version 1.5, and a limit of 512MB on Memory Channel Version 2.0.
It is desirable before running a PVM program to increase the default values. Increasing the default values does not use up memory resources but allows PVM to access more Memory Channel space later.
To increase from the default 10MB allocation on each host, for example to 100MB, follow one of these steps:
Edit the /etc/rc.config file and modify the IMC_MAXALLOC and IMC_MAXRECV entries to read:
It is recommended that you increase these values to the maximum allowed for your configuration.
If a number of users are running Compaq PVM applications, it may be desirable to increase the semaphore limits. The parameter sem-mni controls the maximum number of semaphores set system-wide. The default value of the parameter is 16. Each PVM virtual machine uses five semaphores.
To increase the value of the parameter, follow these steps:
[Contents] [Preface] [Chapter 2] [Index]
Copyright © 1999, Digital Equipment Corporation. All rights reserved. Unpublished rights reserved under the copyright laws of the United States.