On Mon, Feb 19, 2024 at 11:08:54AM +0900 Byungchul Park wrote: > 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. > We clearly have dst_cpu when we call this so I still think a check could be done farther up. But this one still looks reasonable to me. Thanks, Phil Reviewed-by: Phil Auld <pauld@xxxxxxxxxx> > 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 > --
