On Mon, Jan 23, 2017 at 01:16:40PM -0500, Johannes Weiner wrote: > Dirty pages can easily reach the end of the LRU while there are still > clean pages to reclaim around. Don't let kswapd write them back just > because there are a lot of them. It costs more CPU to find the clean > pages, but that's almost certainly better than to disrupt writeback > from the flushers with LRU-order single-page writes from reclaim. And > the flushers have been woken up by that point, so we spend IO capacity > on flushing and CPU capacity on finding the clean cache. > > Only start writing dirty pages if they have cycled around the LRU > twice now and STILL haven't been queued on the IO device. It's > possible that the dirty pages are so sparsely distributed across > different bdis, inodes, memory cgroups, that the flushers take forever > to get to the ones we want reclaimed. Once we see them twice on the > LRU, we know that's the quicker way to find them, so do LRU writeback. > > Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Mel Gorman <mgor...@suse.de> -- Mel Gorman SUSE Labs
