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s=arc-20220608; t=1708069563; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=q7bomlDDmexTZ7YWVussTv6imGEbYGh2gEdB82BWe7k=; b=MuLQM2Lpbd7EoMbfpPPVmnVJqKuTp46PDqW5/7iCZyNNse6oxI4OEYH2lmZDzihkAs9UBT wwIgoa0hlOp585T9KIDThmLx7QoiLucjabapIedt+3io2+mILcfhO1pSO+YE+oaa++vwBo lzjSHIZym+CBBXPw604D3reMndsKE8E= X-AuditID: a67dfc5b-d85ff70000001748-62-65cf12b5bc6e Date: Fri, 16 Feb 2024 16:45:51 +0900 From: Byungchul Park To: Phil Auld Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org Subject: Re: [PATCH] sched/numa, mm: do not promote folios to nodes not set N_MEMORY Message-ID: <20240216074551.GD32626@system.software.com> References: <20240214035355.18335-1-byungchul@sk.com> <20240214123137.GA70927@lorien.usersys.redhat.com> <20240214200318.GA74174@lorien.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; 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It's because of null pointers of ->zone_pgdat of zones of > > > those nodes that are not initialized at booting time. So should avoid > > > nodes not set N_MEMORY from getting promoted. > > > > > > > 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: > > > > > > > > ? __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 > > > > > > > > Modules linked in: > > > > CR2: 00000000000033f3 > > > > ---[ end trace 0000000000000000 ]--- > > > > 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 > > > > note: masim[895] exited with irqs disabled > > > > I think you could trim the down a little bit. > > > > > > > > > > Signed-off-by: Byungchul Park > > > Reported-by: hyeongtak.ji@sk.com > > > --- > > > kernel/sched/fair.c | 17 +++++++++++++++++ > > > 1 file changed, 17 insertions(+) > > > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > > index d7a3c63a2171..6d215cc85f14 100644 > > > --- a/kernel/sched/fair.c > > > +++ b/kernel/sched/fair.c > > > @@ -1828,6 +1828,23 @@ 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. What's even worse, oops > > > + * can be observed by the null pointer of ->zone_pgdat in > > > + * various points of the code during migration. > > > + * > > > > > + * For instance, oops has been observed at CPU2 while qemu'ing: > > > + * > > > + * {qemu} \ > > > + * -numa node,nodeid=0,mem=1G,cpus=0-1 \ > > > + * -numa node,nodeid=1,cpus=2-3 \ > > > + * -numa node,nodeid=2,mem=8G \ > > > + * ... > > > > This part above should probably be in the commit message not in the code. > > The first paragraph of comment is plenty. > > > > Otherwise, I think the check probably makes sense. > > > > Actually, after looking at the memory.c code I wonder if this check should > not be made farther up in the numa migrate machinery. First of all, we cannot avoid hinting fault. It's because no one knows which node a task eventually runs on until a hinting fault occurs. So should let it go get hinting fault *and then* we can make the decision if we can migrate the folio or not. Assuming that, IMHO, should_numa_migrate_memory() is a good place to make it. Thoughts? Am I missing something? Byungchul > Cheers, > Phil > > > > > Cheers, > > Phil > > > > > + */ > > > + 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. > > > -- > > > 2.17.1 > > > > > > > > > > -- > > > > > > --