NAME¶
sge_ckpt.1 - the Sun Grid Engine checkpointing mechanism and checkpointing
support
DESCRIPTION¶
Sun Grid Engine supports two levels of checkpointing: the user level and a
operating system provided transparent level. User level checkpointing refers
to applications, which do their own checkpointing by writing restart files at
certain times or algorithmic steps and by properly processing these restart
files when restarted.
Transparent checkpointing has to be provided by the operating system and is
usually integrated in the operating system kernel. An example for a kernel
integrated checkpointing facility is the Hibernator package from Softway for
SGI IRIX platforms.
Checkpointing jobs need to be identified to the Sun Grid Engine system by using
the
-ckpt option of the command. The argument to this flag refers to a
so called checkpointing environment, which defines the attributes of the
checkpointing method to be used (see for details). Checkpointing environments
are setup by the options
-ackpt,
-dckpt,
-mckpt and
-sckpt. The option
-c can be used to overwrite the
when
attribute for the referenced checkpointing environment.
If a queue is of the type CHECKPOINTING, jobs need to have the checkpointing
attribute flagged (see the
-ckpt option to to be permitted to run in
such a queue. As opposed to the behavior for regular batch jobs, checkpointing
jobs are aborted under conditions, for which batch or interactive jobs are
suspended or even stay unaffected. These conditions are:
- •
- Explicit suspension of the queue or job via by the cluster
administration or a queue owner if the x occasion specifier (see
-c and was assigned to the job.
- •
- A load average value exceeding the suspend threshold as
configured for the corresponding queues (see
- •
- Shutdown of the Sun Grid Engine execution daemon being
responsible for the checkpointing job.
After abortion, the jobs will migrate to other queues unless they were submitted
to one specific queue by an explicit user request. The migration of jobs leads
to a dynamic load balancing.
Note: The abortion of checkpointed jobs
will free all resources (memory, swap space) which the job occupies at that
time. This is opposed to the situation for suspended regular jobs, which still
cover swap space.
RESTRICTIONS¶
When a job migrates to a queue on another machine at present no files are
transferred automatically to that machine. This means that all files which are
used throughout the entire job including restart files, executables and
scratch files must be visible or transferred explicitly (e.g. at the beginning
of the job script).
There are also some practical limitations regarding use of disk space for
transparently checkpointing jobs. Checkpoints of a transparently checkpointed
application are usually stored in a checkpoint file or directory by the
operating system. The file or directory contains all the text, data, and stack
space for the process, along with some additional control information. This
means jobs which use a very large virtual address space will generate very
large checkpoint files. Also the workstations on which the jobs will actually
execute may have little free disk space. Thus it is not always possible to
transfer a transparent checkpointing job to a machine, even though that
machine is idle. Since large virtual memory jobs must wait for a machine that
is both idle, and has a sufficient amount of free disk space, such jobs may
suffer long turnaround times.
SEE ALSO¶
Sun Grid Engine Installation and Administration Guide, Sun Grid Engine
User's Guide
COPYRIGHT¶
See for a full statement of rights and permissions.