On Fri, Feb 16, 2024 at 02:51:24PM +0100, Oscar Salvador wrote: > On Fri, Feb 16, 2024 at 08:40:45PM +0900, Byungchul Park wrote: > > From 150af2f78e19217a1d03e47e3ee5279684590fb4 Mon Sep 17 00:00:00 2001 > > From: Byungchul Park <byungchul@xxxxxx> > > Date: Fri, 16 Feb 2024 20:18:10 +0900 > > Subject: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY > > "do not try to promote folios to memoryless nodes" Thank you. I will. > because AFAICS we are just trying. > Even if should_numa_migrate_memory() returns true, I assume that we will > fail somewhere down the chain e.g: migrate_pages() when we see that this > node does not any memory, right? Yes. > > A numa node might not have its local memory but CPUs. Promoting a folio > > to the node's local memory is nonsense. So avoid nodes not set N_MEMORY > > from getting promoted. > > If you talk about memoryless nodes everybody gets it better IMHO. > "Memoryless nodes do not have any memory to migrate to, so stop trying it." Much better. > > Signed-off-by: Byungchul Park <byungchul@xxxxxx> > > --- > > kernel/sched/fair.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index d7a3c63a2171..7ed9ef3c0134 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -1828,6 +1828,13 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, > > int dst_nid = cpu_to_node(dst_cpu); > > int last_cpupid, this_cpupid; > > > > + /* > > + * A node of dst_nid might not have its local memory. Promoting > > + * a folio to the node is meaningless. > > + */ > > + if (!node_state(dst_nid, N_MEMORY)) > > + return false; > > "Cannot migrate to memoryless nodes" > > seems shorter and more clear. Agree. Byungchul > So, what happens when we return true here? will we fail at > migrate_pages() I guess? That is quite down the road so I guess > this check can save us some time. > > > -- > Oscar Salvador > SUSE Labs
