[PATCH] kswapd throttling fixes
The logic in balance_pgdat() is all bollixed up. - the incoming arg `nr_pages' should be used to determine if we're being asked to free a specific number of pages, not `to_free'. - local variable `to_free' is not appropriate for the determination of whether we failed to bring all zones to appropriate free pages levels. Fix this by correctly calculating `all_zones_ok' and then use all_zones_ok to determine whether we need to throttle kswapd. So the logic now is: for (increasing priority) { all_zones_ok = 1; for (all zones) { to_reclaim = number of pages to try to reclaim from this zone; max_scan = number of pages to scan in this pass (gets larger as `priority' decreases) /* * set `reclaimed' to the number of pages which were * actually freed up */ reclaimed = scan(max_scan pages); reclaimed += shrink_slab(); to_free -= reclaimed; /* for the `nr_pages>0' case */ /* * If this scan failed to reclaim `to_reclaim' or more * pages, we're getting into trouble. Need to scan * some more, and throttle kswapd. Note that this * zone may now have sufficient free pages due to * freeing activity by some other process. That's * OK - we'll pick that info up on the next pass * through the loop. */ if (reclaimed < to_reclaim) all_zones_ok = 0; } if (to_free > 0) continue; /* swsusp: need to do more work */ if (all_zones_ok) break; /* kswapd is done */ /* * OK, kswapd is getting into trouble. Take a nap, then take * another pass across the zones. */ blk_congestion_wait(); }
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