On January 24, 2017 2:17 AM Johannes Weiner wrote: > > We noticed a regression on multiple hadoop workloads when moving from > 3.10 to 4.0 and 4.6, which involves kswapd getting tangled up in page > writeout, causing direct reclaim herds that also don't make progress. > > I tracked it down to the thrash avoidance efforts after 3.10 that make > the kernel better at keeping use-once cache and use-many cache sorted > on the inactive and active list, with more aggressive protection of > the active list as long as there is inactive cache. Unfortunately, our > workload's use-once cache is mostly from streaming writes. Waiting for > writes to avoid potential reloads in the future is not a good tradeoff. > > These patches do the following: > > 1. Wake the flushers when kswapd sees a lump of dirty pages. It's > possible to be below the dirty background limit and still have > cache velocity push them through the LRU. So start a-flushin'. > > 2. Let kswapd only write pages that have been rotated twice. This > makes sure we really tried to get all the clean pages on the > inactive list before resorting to horrible LRU-order writeback. > > 3. Move rotating dirty pages off the inactive list. Instead of > churning or waiting on page writeback, we'll go after clean active > cache. This might lead to thrashing, but in this state memory > demand outstrips IO speed anyway, and reads are faster than writes. > > More details in the individual changelogs. > > include/linux/mm_inline.h | 7 ++++ > include/linux/mmzone.h | 2 -- > include/linux/writeback.h | 2 +- > include/trace/events/writeback.h | 2 +- > mm/swap.c | 9 ++--- > mm/vmscan.c | 68 +++++++++++++++----------------------- > 6 files changed, 41 insertions(+), 49 deletions(-) > Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
