Messages in this thread | | | Date | Mon, 19 Feb 2024 11:26:15 -0800 | From | Davidlohr Bueso <> | Subject | Re: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY |
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On Sun, 18 Feb 2024, Oscar Salvador 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@sk.com> >> > 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" > >Thinking some more, promote might be misleading, just something like >"do not try to migrate memory to memoryless nodes".
Yes. Does this also want an unlikely()? Not that it would be measurable.
>As this is not a bug fix but an optimization, as we will fail anyways >in migrate_misplaced_folio() when migrate_balanced_pgdat() notices that >we do not have any memory on that code.
This should be in the changelog and the subject is misleading as well.
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> >With the other comments addressed: > >Reviewed-by: Oscar Salvador <osalvador@suse.de> > >> >> 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? >> >> > 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." >> >> >> > Signed-off-by: Byungchul Park <byungchul@sk.com> >> > --- >> > 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. >> >> 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 >> > >-- >Oscar Salvador >SUSE Labs >
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