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Application killed with signal 7 (memory alignment error)

Some users may find that some Blue Gene/P jobs exit with a segmentation fault and signal 7 (SIGBUS). This is due to an undocumented feature on the Blue Gene/P that deals with memory alignment during I/O operations. This feature allows the user to set a memory alignment error threshold for I/O operations in their job but results in confusion due to it's default value of 1000. This threshold can be controlled using an environment variable.

Die as soon as a memory alignment error is encountered during I/O:

-env BG_MAXALIGNEXP=1

Silence all memory alignment errors during I/O:

-env BG_MAXALIGNEXP=-1

Configure a threshold to workaround occasional memory alignment errors during I/O (eg. 2000 in this case):

-env BG_MAXALIGNEXP=2000

Note that memory alignment errors during I/O do have the potential to reduce I/O performance and as such it is better to eliminate them rather than ignore them if possible.


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