Implement fix for missing i/o values #174
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Under some circumstances that are not very well understood the process tree chain loses i/o values (which would normally always be "inherited" by parent processes as children exit). To compensate for this the iomon module will now record maximum i/o stats, and if the polled values are below these it will replace the stats with the previous maximums. A warning is also printed. To test this logic there is a defined variable in iomon.cpp that switches on code that artificially provokes the problem, exercising the recovery logic.
amete
approved these changes
Oct 27, 2020
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Thanks a lot @graeme-a-stewart. I don't see any issue with this patch as the disk I/O metrics should really be monotonically increasing. It's technically working as expected, too. Having said that, the cause of the issue in #173 is still not clear to me. In any case, this is a fair workaround.
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Under some circumstances that are not very well
understood the process tree chain loses i/o values
(which would normally always be "inherited" by
parent processes as children exit).
To compensate for this the iomon module will now
record maximum i/o stats, and if the polled values
are below these it will replace the stats with the
previous maximums. A warning is also printed.
To test this logic there is a defined variable in
iomon.cpp that switches on code that artificially
provokes the problem, exercising the recovery
logic.
Closes #173