20b51af1 - mm/migrate: add sysfs interface to enable reclaim migration

Thu, 02 Sep 2021 21:59:33 +0000

mm/migrate: add sysfs interface to enable reclaim migrationSome method is obviously needed to enable reclaim-based migration.Just like traditional autonuma, there will be some workloads that willbenefit like workloads with more "static" configurations where hot pagesstay hot and cold pages stay cold. If pages come and go from the hot andcold sets, the benefits of this approach will be more limited.The benefits are truly workload-based and *not* hardware-based. We do notbelieve that there is a viable threshold where certain hardwareconfigurations should have this mechanism enabled while others do not.To be conservative, earlier work defaulted to disable reclaim- basedmigration and did not include a mechanism to enable it. This proposes adda new sysfs file /sys/kernel/mm/numa/demotion_enabledas a method to enable it.We are open to any alternative that allows end users to enable thismechanism or disable it if workload harm is detected (just liketraditional autonuma).Once this is enabled page demotion may move data to a NUMA node that doesnot fall into the cpuset of the allocating process. This could beconstrued to violate the guarantees of cpusets. However, since this is anopt-in mechanism, the assumption is that anyone enabling it is content torelax the guarantees.Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.comLink: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.comSigned-off-by: Huang Ying Originally-by: Dave Hansen Cc: Michal Hocko Cc: Wei Xu Cc: Yang Shi Cc: Zi Yan Cc: David Rientjes Cc: Dan Williams Cc: David Hildenbrand Cc: Greg Thelen Cc: Keith Busch Cc: Oscar Salvador Cc: Yang Shi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds List of files: /linux-6.15/Documentation/ABI/testing/sysfs-kernel-mm-numa

Changes in sysfs-kernel-mm-numa

20b51af1 - mm/migrate: add sysfs interface to enable reclaim migration