On 10/03/2012 07:51 PM, Andrea Arcangeli wrote:
+/*
+ * In this function we build a temporal CPU_node<->page relation by
+ * using a two-stage autonuma_last_nid filter to remove short/unlikely
+ * relations.
+ *
+ * Using P(p) ~ n_p / n_t as per frequentest probability, we can
+ * equate a node's CPU usage of a particular page (n_p) per total
+ * usage of this page (n_t) (in a given time-span) to a probability.
+ *
+ * Our periodic faults will then sample this probability and getting
+ * the same result twice in a row, given these samples are fully
+ * independent, is then given by P(n)^2, provided our sample period
+ * is sufficiently short compared to the usage pattern.
+ *
+ * This quadric squishes small probabilities, making it less likely
+ * we act on an unlikely CPU_node<->page relation.
+ */
+static inline bool last_nid_set(struct page *page, int this_nid)
+{
Could be nice to rename this function to should_migrate_page()...
+ bool ret = true;
+ int autonuma_last_nid = ACCESS_ONCE(page->autonuma_last_nid);
+ VM_BUG_ON(this_nid < 0);
+ VM_BUG_ON(this_nid >= MAX_NUMNODES);
+ if (autonuma_last_nid != this_nid) {
+ if (autonuma_last_nid >= 0)
+ ret = false;
+ ACCESS_ONCE(page->autonuma_last_nid) = this_nid;
+ }
+ return ret;
+}
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