linux-kernel - Re: [RFC PATCH V0 0/10] mm: slowtier page promotion based on PTE A bit

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Message-ID: <20250212170212.f5coa462p75fuqj6@offworld>
Date: Wed, 12 Feb 2025 09:02:12 -0800
From: Davidlohr Bueso <dave@...olabs.net>
To: Raghavendra K T <raghavendra.kt@....com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, gourry@...rry.net,
	nehagholkar@...a.com, abhishekd@...a.com, david@...hat.com,
	ying.huang@...el.com, nphamcs@...il.com, akpm@...ux-foundation.org,
	hannes@...xchg.org, feng.tang@...el.com, kbusch@...a.com,
	bharata@....com, Hasan.Maruf@....com, sj@...nel.org,
	willy@...radead.org, kirill.shutemov@...ux.intel.com,
	mgorman@...hsingularity.net, vbabka@...e.cz, hughd@...gle.com,
	rientjes@...gle.com, shy828301@...il.com, Liam.Howlett@...cle.com,
	peterz@...radead.org, mingo@...hat.com
Subject: Re: [RFC PATCH V0 0/10] mm: slowtier page promotion based on PTE A
 bit

On Sun, 01 Dec 2024, Raghavendra K T wrote:

>6. Holding PTE lock before migration.

fyi I tried testing this series with 'perf-bench numa mem' and got a soft lockup,
unable to take the PTL (and lost the machine to debug further atm), ie:

[ 3852.217675] CPU: 127 UID: 0 PID: 12537 Comm: watch-numa-sche Tainted: G      D      L     6.14.0-rc2-kmmscand-v1+ #3
[ 3852.217677] Tainted: [D]=DIE, [L]=SOFTLOCKUP
[ 3852.217678] RIP: 0010:native_queued_spin_lock_slowpath+0x64/0x290
[ 3852.217683] Code: 77 7b f0 0f ba 2b 08 0f 92 c2 8b 03 0f b6 d2 c1 e2 08 30 e4 09 d0 3d ff 00 00 00 77 57 85 c0 74 10 0f b6 03 84 c0 74 09 f3 90 <0f> b6 03 84 c0 75 f7 b8 01 00 00 00 66 89 03 5b 5d 41 5c 41 5d c3
[ 3852.217684] RSP: 0018:ff274259b3c9f988 EFLAGS: 00000202
[ 3852.217685] RAX: 0000000000000001 RBX: ffbd2efd8c08c9a8 RCX: 000ffffffffff000
[ 3852.217686] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffbd2efd8c08c9a8
[ 3852.217687] RBP: ff161328422c1328 R08: ff274259b3c9fb90 R09: ff161328422c1000
[ 3852.217688] R10: 00000000ffffffff R11: 0000000000000004 R12: 00007f52cca00000
[ 3852.217688] R13: ff274259b3c9fa00 R14: ff16132842326000 R15: ff161328422c1328
[ 3852.217689] FS:  00007f32b6f92b80(0000) GS:ff161423bfd80000(0000) knlGS:0000000000000000
[ 3852.217691] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3852.217692] CR2: 0000564ddbf68008 CR3: 00000080a81cc005 CR4: 0000000000773ef0
[ 3852.217693] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 3852.217694] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[ 3852.217694] PKRU: 55555554
[ 3852.217695] Call Trace:
[ 3852.217696]  <IRQ>
[ 3852.217697]  ? watchdog_timer_fn+0x21b/0x2a0
[ 3852.217699]  ? __pfx_watchdog_timer_fn+0x10/0x10
[ 3852.217702]  ? __hrtimer_run_queues+0x10f/0x2a0
[ 3852.217704]  ? hrtimer_interrupt+0xfb/0x240
[ 3852.217706]  ? __sysvec_apic_timer_interrupt+0x4e/0x110
[ 3852.217709]  ? sysvec_apic_timer_interrupt+0x68/0x90
[ 3852.217712]  </IRQ>
[ 3852.217712]  <TASK>
[ 3852.217713]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
[ 3852.217717]  ? native_queued_spin_lock_slowpath+0x64/0x290
[ 3852.217720]  _raw_spin_lock+0x25/0x30
[ 3852.217723]  __pte_offset_map_lock+0x9a/0x110
[ 3852.217726]  gather_pte_stats+0x1e3/0x2c0
[ 3852.217730]  walk_pgd_range+0x528/0xbb0
[ 3852.217733]  __walk_page_range+0x71/0x1d0
[ 3852.217736]  walk_page_vma+0x98/0xf0
[ 3852.217738]  show_numa_map+0x11a/0x3a0
[ 3852.217741]  seq_read_iter+0x2a6/0x470
[ 3852.217745]  seq_read+0x12b/0x170
[ 3852.217748]  vfs_read+0xe0/0x370
[ 3852.217751]  ? syscall_exit_to_user_mode+0x49/0x210
[ 3852.217755]  ? do_syscall_64+0x8a/0x190
[ 3852.217758]  ksys_read+0x6a/0xe0
[ 3852.217762]  do_syscall_64+0x7e/0x190
[ 3852.217765]  ? __memcg_slab_free_hook+0xd4/0x120
[ 3852.217768]  ? __x64_sys_close+0x38/0x80
[ 3852.217771]  ? kmem_cache_free+0x3bf/0x3e0
[ 3852.217774]  ? syscall_exit_to_user_mode+0x49/0x210
[ 3852.217777]  ? do_syscall_64+0x8a/0x190
[ 3852.217780]  ? do_syscall_64+0x8a/0x190
[ 3852.217783]  ? __irq_exit_rcu+0x3e/0xe0
[ 3852.217785]  entry_SYSCALL_64_after_hwframe+0x76/0x7e