Re: [PATCH v4] sched/numa, mm: do not try to migrate memory to memoryless nodes

[Andrew Morton]

On Mon, 19 Feb 2024 16:43:36 +0800 "Huang, Ying" <ying.huang@xxxxxxxxx> wrote:

> > +	/*
> > +	 * Cannot migrate to memoryless nodes.
> > +	 */
> > +	if (!node_state(dst_nid, N_MEMORY))
> > +		return false;
> > +
> >  	/*
> >  	 * The pages in slow memory node should be migrated according
> >  	 * to hot/cold instead of private/shared.
> 
> Good catch!
> 
> IIUC, you will use patch as fix to the issue in
> 
> https://lore.kernel.org/lkml/20240216111502.79759-1-byungchul@xxxxxx/
> 
> If so, we need the Fixes: tag to make it land in -stable properly.

Yes, this changelog is missing rather a lot of important information.

I pulled together the below, please check.


From: Byungchul Park <byungchul@xxxxxx>
Subject: sched/numa, mm: do not try to migrate memory to memoryless nodes
Date: Mon, 19 Feb 2024 13:10:47 +0900

With numa balancing on, when a numa system is running where a numa node
doesn't have its local memory so it has no managed zones, the following
oops has been observed.  It's because wakeup_kswapd() is called with a
wrong zone index, -1.  Fixed it by checking the index before calling
wakeup_kswapd().

> BUG: unable to handle page fault for address: 00000000000033f3
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 2 PID: 895 Comm: masim Not tainted 6.6.0-dirty #255
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>    rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> RIP: 0010:wakeup_kswapd (./linux/mm/vmscan.c:7812)
> Code: (omitted)
> RSP: 0000:ffffc90004257d58 EFLAGS: 00010286
> RAX: ffffffffffffffff RBX: ffff88883fff0480 RCX: 0000000000000003
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88883fff0480
> RBP: ffffffffffffffff R08: ff0003ffffffffff R09: ffffffffffffffff
> R10: ffff888106c95540 R11: 0000000055555554 R12: 0000000000000003
> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88883fff0940
> FS:  00007fc4b8124740(0000) GS:ffff888827c00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000033f3 CR3: 000000026cc08004 CR4: 0000000000770ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554
> Call Trace:
>  <TASK>
> ? __die
> ? page_fault_oops
> ? __pte_offset_map_lock
> ? exc_page_fault
> ? asm_exc_page_fault
> ? wakeup_kswapd
> migrate_misplaced_page
> __handle_mm_fault
> handle_mm_fault
> do_user_addr_fault
> exc_page_fault
> asm_exc_page_fault
> RIP: 0033:0x55b897ba0808
> Code: (omitted)
> RSP: 002b:00007ffeefa821a0 EFLAGS: 00010287
> RAX: 000055b89983acd0 RBX: 00007ffeefa823f8 RCX: 000055b89983acd0
> RDX: 00007fc2f8122010 RSI: 0000000000020000 RDI: 000055b89983acd0
> RBP: 00007ffeefa821a0 R08: 0000000000000037 R09: 0000000000000075
> R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
> R13: 00007ffeefa82410 R14: 000055b897ba5dd8 R15: 00007fc4b8340000
>  </TASK>

Fix this by avoiding any attempt to migrate memory to memoryless nodes.

Link: https://lkml.kernel.org/r/20240219041920.1183-1-byungchul@xxxxxx
Link: https://lkml.kernel.org/r/20240216111502.79759-1-byungchul@xxxxxx
Fixes: c574bbe917036 ("NUMA balancing: optimize page placement for memory tiering system")
Signed-off-by: Byungchul Park <byungchul@xxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>
Cc: Benjamin Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/sched/fair.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/kernel/sched/fair.c~sched-numa-mm-do-not-try-to-migrate-memory-to-memoryless-nodes
+++ a/kernel/sched/fair.c
@@ -1831,6 +1831,12 @@ bool should_numa_migrate_memory(struct t
 	int last_cpupid, this_cpupid;
 
 	/*
+	 * Cannot migrate to memoryless nodes.
+	 */
+	if (!node_state(dst_nid, N_MEMORY))
+		return false;
+
+	/*
 	 * The pages in slow memory node should be migrated according
 	 * to hot/cold instead of private/shared.
 	 */
_