When should a process be migrated?
Posted Oct 8, 2004 16:57 UTC (Fri) by giraffedata
Parent article: When should a process be migrated?
This is measuring a red herring. Apparently, the method uses the "cost to move a process" number -- 5ms and 87ms in the example -- as the cache_hot_time. The two numbers have nothing to do with each other. cache_hot_time is about determining how likely it is that a process has stuff in cache. If it does, there's reason to try to keep it on the same CPU; if not, moving it is free.
What it costs to move a process is another parameter that one could use in conjunction with cache_hot_time to weight the decision whether or not to move a process.
A self-tuning cache_hot_time, on the other hand, would look like this: Keep a process running that regularly accesses some typical amount of memory and sleeps for varying times. Keep it on the same CPU. Have it determine each time it wakes up, by timing, if its memory was still cached. If it was, then cache_hot_time should be greater than the most recent sleep time; if not, it should be less.
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