From: "Christoph Lameter" <clameter@xxxxxxx> > Would it not be much simpler to use the SLIT table to estimate the > migration costs? If the architecture has a SLIT, perhaps yes. The current algorithm is very empirical: for a given pair of CPUs, dirty the L2 cache, migrate the task to the 2nd CPU, then measure how long it takes to redirty the data. The SLIT can give you some metric of "distance" between two CPUs or two nodes, but the scheduler is looking for something it deems directly related to the effects of migrating a cache-hot task. Again, my problem with the migration_cost is that it is expensive to calculate, and that the calculation takes pains to be accurate to within 10-20%, and yet it makes assumptions (e.g., that the migration cost between cpu0 and cpu1 is the same as between cpu0 and cpu31) that make its usefulness questionable. John Hawkes - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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