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MulticoreBSP for C
Version 2.0.4
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MulticoreBSP for C supports checkpointing via the DMTCP software package. More...
Functions | |
| void | mcbsp_checkpoint (void) |
| Synchronises all processes and performs a global checkpointing step. More... | |
| void | mcbsp_enable_checkpoints (void) |
| Enables automatic checkpointing. More... | |
| void | mcbsp_disable_checkpoints (void) |
| Disables automatic checkpointing. More... | |
| void | mcbsp_set_checkpoint_frequency (size_t _cp_f) |
| Allows the user to directly set the checkpointing frequency. More... | |
| size_t | mcbsp_get_checkpoint_frequency (void) |
| Gets the currently active checkpointing frequency. More... | |
| void | mcbsp_set_safe_checkpoint_frequency (size_t _safe_cp_f) |
| Allows the user to set the safe checkpointing frequency. More... | |
| size_t | mcbsp_get_safe_checkpoint_frequency (void) |
| Gets the currently active safe checkpointing frequency. More... | |
MulticoreBSP for C supports checkpointing via the DMTCP software package.
Checkpointing can occur in one of two modes:
Checkpoint is only supported on Linux OSes. Full details follow in the below:
For example use, see examples/checkpointed_loop.c.
Before building, first enable DMTCP in your include.mk file. Then, (re-)build MulticoreBSP for C, and (re-) build the examples; the checkpointed_loop program should now be built automatically. There are two ways to run the checkpointed_loop: 1) issue `dmtcp_launch ./checkpointed_loop', or 2) start `dmtcp_coordinator' as a separate process, and issue `dmtcp_checkpoint ./checkpointed_loop' This runs the calculation once, and successfully, while writing one checkpoint halfway through the computation. To restart from the saved checkpoint, simply issue `dmtcp_restart ckpt_checkpointed_loop_<...>'. The brackets <...> contain an identifier that depends on the instance of your run.
MCBSP_DEFAULT_CHECKPOINT_FREQUENCY created, and set to 0 (=no automatic checkpointing). The machine.info file now takes a new key-value `checkpoint_frequency' which should be followed by a positive integer C. If C > 0, then MulticoreBSP automatically checkpoints every C bsp_syncs. The currently active checkpointing frequency can be read with mcbsp_get_checkpointing_frequency, and set using mcbsp_set_checkpointing_frequency, both defined in `mcbsp-resiliency.h'. These values can be get and set during run-time, before bsp_init, within an SPMD section, and in-between. The library optionally also supports an increased checkpointing frequency when failure is imminent. It relies on an auxiliary daemon to create a file named `/etc/bsp_failure' whenever a part of the hardware fails, or when hardware is detected to become more probable. This file is expected to contain a string that describes the type of hardware trouble detected. When this file is detected to exist, MulticoreBSP switches to a secondary checkpointing frequency defined with key `safe_checkpoint_frequency'. By default, this value equals that of `checkpoint_frequency'. MulticoreBSP for C will also parse the last two lines of `/etc/bsp_failure' and print these to the standard error stream. Other (imminent) hardware failures detections can rely on the same mechanism, but necessarily will depend on auxiliary daemons for failure detection since such detections are highly platform dependent endeavours.
| void mcbsp_checkpoint | ( | void | ) |
Synchronises all processes and performs a global checkpointing step.
To optimise checkpointing performance, users should free all unused or unnecessary memory areas before calling this function. Should MulticoreBSP for C have been compiled without checkpointing support, a call to this primitive will result in an abort of the SPMD run via the bsp_abort primitive.
| void mcbsp_disable_checkpoints | ( | void | ) |
Disables automatic checkpointing.
When automatic checkpointing already was inactive, calling this function has no effect.
| void mcbsp_enable_checkpoints | ( | void | ) |
Enables automatic checkpointing.
When automatic checkpointing was already active, calling this function has no effect.
| size_t mcbsp_get_checkpoint_frequency | ( | void | ) |
Gets the currently active checkpointing frequency.
Will return the frequency that would have been adhered to if checkpointing was active; i.e., even after a mcbsp_disable_checkpointing this function may return a non-zero frequency. A zero frequency means automatic checkpointing is completely disabled.
This function may be called before bsp_init, from within an SPMD section, and anywhere in-between. It will both change the run-time settings (when applicable) as well as change the machine model (i.e., the machine.info).
| size_t mcbsp_get_safe_checkpoint_frequency | ( | void | ) |
Gets the currently active safe checkpointing frequency.
| void mcbsp_set_checkpoint_frequency | ( | size_t | _cp_f | ) |
Allows the user to directly set the checkpointing frequency.
A zero frequency means no automatic checkpointing will be performed. Calling this function with a non-zero frequency is in no way equivalent or including a call to mcbsp_enable_checkpointing; if checkpointing was disabled using mcbsp_disable_checkpointing, a non-zero checkpointing frequency will have no effect until after a next mcbsp_enable_checkpointing.
This function may be called before bsp_init, from within an SPMD section, and anywhere in-between. It will both change the run-time settings (when applicable) as well as change the machine model (i.e., the machine.info).
| _cp_f | The new checkpointing frequency. |
| void mcbsp_set_safe_checkpoint_frequency | ( | size_t | _safe_cp_f | ) |
Allows the user to set the safe checkpointing frequency.
If this value has not been set, it will equal that of the normal checkpointing frequency as may be set by mcbsp_set_checkpoint_frequency. Safe checkpointing only takes effect when the MulticoreBSP for C library detects the existance of the file `/etc/bsp_failure', which indicates hardware failures have occurred, are occurring, or may be imminent. Creation of this file is done by auxiliary daemons, and never by the BSP run-time, since hardware failure detection is a highly platform-dependent endeavour.
| _safe_cp_f | The checkpointing frequency used in case of (imminent) hardware failures. |
1.8.5