As Yang Shi suggested [1], it will be helpful to explain why we should select target node randomly now if there are multiple target nodes. [1] https://lore.kernel.org/all/CAHbLzkqSqCL+g7dfzeOw8fPyeEC0BBv13Ny1UVGHDkadnQdR=g@xxxxxxxxxxxxxx/ Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> --- mm/migrate.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/migrate.c b/mm/migrate.c index 8d39720de4eb..d9af89248196 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1209,6 +1209,14 @@ int next_demotion_node(int node) /* * If there are multiple target nodes, just select one * target node randomly. + * + * In addition, we can also use round-robin to select + * target node, but we should introduce another variable + * for node_demotion[] to record last selected target node, + * that may cause cache ping-pong due to the changing of + * last target node. Or introducing per-cpu data to avoid + * caching issue, which seems more complicated. So selecting + * target node randomly seems better until now. */ index = get_random_int() % target_nr; break; -- 2.27.0
