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authorHuang Ying <ying.huang@intel.com>2021-09-02 14:59:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-03 09:58:16 -0700
commit20b51af15e014cac63b58a4f8b8b323ac35bccce (patch)
tree1c718dff92e64dfef017c46ba2662c844353bce8 /include
parent3a235693d3930e1276c8d9cc0ca5807ef292cf0a (diff)
mm/migrate: add sysfs interface to enable reclaim migration
Some method is obviously needed to enable reclaim-based migration. Just like traditional autonuma, there will be some workloads that will benefit like workloads with more "static" configurations where hot pages stay hot and cold pages stay cold. If pages come and go from the hot and cold sets, the benefits of this approach will be more limited. The benefits are truly workload-based and *not* hardware-based. We do not believe that there is a viable threshold where certain hardware configurations should have this mechanism enabled while others do not. To be conservative, earlier work defaulted to disable reclaim- based migration and did not include a mechanism to enable it. This proposes add a new sysfs file /sys/kernel/mm/numa/demotion_enabled as a method to enable it. We are open to any alternative that allows end users to enable this mechanism or disable it if workload harm is detected (just like traditional autonuma). Once this is enabled page demotion may move data to a NUMA node that does not fall into the cpuset of the allocating process. This could be construed to violate the guarantees of cpusets. However, since this is an opt-in mechanism, the assumption is that anyone enabling it is content to relax the guarantees. Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.com Link: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.com Signed-off-by: Huang Ying <ying.huang@intel.com> Originally-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Wei Xu <weixugc@google.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Cc: Zi Yan <ziy@nvidia.com> Cc: David Rientjes <rientjes@google.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: Keith Busch <kbusch@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Yang Shi <shy828301@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mempolicy.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 0aaf91b496e2..4ca025e2a77e 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -184,6 +184,8 @@ extern bool vma_migratable(struct vm_area_struct *vma);
extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned long);
extern void mpol_put_task_policy(struct task_struct *);
+extern bool numa_demotion_enabled;
+
#else
struct mempolicy {};
@@ -292,5 +294,7 @@ static inline nodemask_t *policy_nodemask_current(gfp_t gfp)
{
return NULL;
}
+
+#define numa_demotion_enabled false
#endif /* CONFIG_NUMA */
#endif