I've been sitting on these for too long. Tha main purpose of this post is to have a public discussion with the other folks who are interested in this functionalty and converge on a single implementation. This set directly incorporates a statictics patch from Yang Shi and also includes one to ensure good behavior with cgroup reclaim which was very closely derived from this series: https://lore.kernel.org/linux-mm/1560468577-101178-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx/ Since the last post, the major changes are: - Added patch to skip migration when doing cgroup reclaim - Added stats patch from Yang Shi The full series is also available here: https://github.com/hansendc/linux/tree/automigrate-20200629 -- We're starting to see systems with more and more kinds of memory such as Intel's implementation of persistent memory. Let's say you have a system with some DRAM and some persistent memory. Today, once DRAM fills up, reclaim will start and some of the DRAM contents will be thrown out. Allocations will, at some point, start falling over to the slower persistent memory. That has two nasty properties. First, the newer allocations can end up in the slower persistent memory. Second, reclaimed data in DRAM are just discarded even if there are gobs of space in persistent memory that could be used. This set implements a solution to these problems. At the end of the reclaim process in shrink_page_list() just before the last page refcount is dropped, the page is migrated to persistent memory instead of being dropped. While I've talked about a DRAM/PMEM pairing, this approach would function in any environment where memory tiers exist. This is not perfect. It "strands" pages in slower memory and never brings them back to fast DRAM. Other things need to be built to promote hot pages back to DRAM. This is part of a larger patch set. If you want to apply these or play with them, I'd suggest using the tree from here. It includes autonuma-based hot page promotion back to DRAM: http://lkml.kernel.org/r/c3d6de4d-f7c3-b505-2e64-8ee5f70b2118@xxxxxxxxx This is also all based on an upstream mechanism that allows persistent memory to be onlined and used as if it were volatile: http://lkml.kernel.org/r/20190124231441.37A4A305@xxxxxxxxxxxxxxxxxx Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> -- Dave Hansen (5): mm/numa: node demotion data structure and lookup mm/vmscan: Attempt to migrate page in lieu of discard mm/numa: automatically generate node migration order mm/vmscan: never demote for memcg reclaim mm/numa: new reclaim mode to enable reclaim-based migration Keith Busch (2): mm/migrate: Defer allocating new page until needed mm/vmscan: Consider anonymous pages without swap Yang Shi (1): mm/vmscan: add page demotion counter Documentation/admin-guide/sysctl/vm.rst | 9 include/linux/migrate.h | 6 include/linux/node.h | 9 include/linux/vm_event_item.h | 2 include/trace/events/migrate.h | 3 mm/debug.c | 1 mm/internal.h | 1 mm/migrate.c | 400 ++++++++++++++++++++++++++------ mm/page_alloc.c | 2 mm/vmscan.c | 88 ++++++- mm/vmstat.c | 2 11 files changed, 439 insertions(+), 84 deletions(-)
