On Mon, Jun 06, 2016 at 03:48:34PM -0400, Johannes Weiner wrote: > Operations like MADV_FREE, FADV_DONTNEED etc. currently move any > affected active pages to the inactive list to accelerate their reclaim > (good) but also steer page reclaim toward that LRU type, or away from > the other (bad). > > The reason why this is undesirable is that such operations are not > part of the regular page aging cycle, and rather a fluke that doesn't > say much about the remaining pages on that list. They might all be in > heavy use. But once the chunk of easy victims has been purged, the VM > continues to apply elevated pressure on the remaining hot pages. The > other LRU, meanwhile, might have easily reclaimable pages, and there > was never a need to steer away from it in the first place. > > As the previous patch outlined, we should focus on recording actually > observed cost to steer the balance rather than speculating about the > potential value of one LRU list over the other. In that spirit, leave > explicitely deactivated pages to the LRU algorithm to pick up, and let > rotations decide which list is the easiest to reclaim. > > Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Nice description. Agreed. Acked-by: Minchan Kim <minc...@kernel.org>
