NAME

migd − Manage the migration load average and idle time database

SYNOPSIS

migd [−s] [−D debugLevel] [−L] [−F]

OPTIONS

−sRun in “silent” mode, in which case messages about evictions are not displayed in the syslog.   The default is to print a message about each process evicted. 

−D debugLevelSet the level of debugging messages.  The default is 0, which means only severe errors are printed.  Higher debugging levels produce more informational and debugging output to stderr. 

−LLog errors to files.  Rather than using the inherited stderr, migd will append messages to the file /sprite/admin/migd/$HOST.log, and the global daemon will write to /sprite/admin/migd/global-log. 

−FDon’t fork; do all commands in a single process.  For debugging purposes. 

INTRODUCTION

This command is used to manage the migration load average and idle time database.  A centralized daemon keeps track of all hosts and assigns idle hosts to processes upon request.  The interface to access the migration daemon is in the Mig library.  Each host runs a copy of the migration daemon, which reports periodically to the central daemon.  The per-host daemon is responsible for sampling the load average and for detecting when foreign processes should be evicted --- i.e., migrated elsewhere --- when a user returns.  The per-host daemon also responds to read requests on a pseudo-device in its host-specific directory, in which case it returns a Mig_Info structure that may be used to obtain the current load averages. 

The global daemon is responsible for keeping track of which processes are using which hosts.  When an eviction occurs, the daemon notifies the process that had been using the host to inform it that the host is no longer available.  If a process requests more hosts than are available, then when additional hosts are available the daemon notifies the process that it may try to request more hosts. 

If the global daemon is killed, or its host fails, one of the per-host instances of migd will fork a process to become the new global daemon.  User processes will lose their connection to the global daemon.  The Mig library is responsible for reestablishing the connection.  The new global daemon will restore its state from a checkpoint file in order to have an approximation of the last time each host was known to be up.  Hosts are assumed to be down until their migration daemons contact the new global daemon. 

SEE ALSO

mig, loadavg, pmake, migcmd, xload

FILES

/sprite/admin/migd/global-log
The global migration daemon error log.

/sprite/admin/migd/$HOST.log
The error log used by host $HOST.

/sprite/admin/migd/pdev
The pseudo-device used to communicate with the global daemon.

/hosts/$HOST/migd.pdev
The pseudo-device used to communicate with the local daemon.

/sprite/admin/migd/check
The file used to store the most recent information about host uptimes.

KEYWORDS

database, eviction, foreign, idle time, load average, process migration, uptime

Sprite version 1.0  —  December 06, 1990