On 2024/6/25 9:17, Huang, Ying wrote: > Hi, Zhenneng, > > Zhenneng Li <lizhenneng@xxxxxxxxxx> writes: > >> We restrict the number of pages to be migrated to no more than >> HPAGE_PMD_NR or NR_MAX_BATCHED_MIGRATION, but in fact, the >> number of pages to be migrated may reach 2*HPAGE_PMD_NR-1 or 2 >> *NR_MAX_BATCHED_MIGRATION-1, it's not in inconsistent with the context. > > Yes. It's not HPAGE_PMD_NR exactly. > >> Please refer to the patch: 42012e0436d4(migrate_pages: restrict number >> of pages to migrate in batch) >> >> Signed-off-by: Zhenneng Li <lizhenneng@xxxxxxxxxx> >> --- >> mm/migrate.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 781979567f64..7a4b37aac9e8 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1961,7 +1961,7 @@ int migrate_pages(struct list_head *from, new_folio_t get_new_folio, >> break; >> } >> if (nr_pages >= NR_MAX_BATCHED_MIGRATION) >> - list_cut_before(&folios, from, &folio2->lru); >> + list_cut_before(&folios, from, &folio->lru); > > If the first entry of the list "from" is a THP with size HPAGE_PMD_NR, > "folio" will be the first entry of from, so that "folios" will be empty. > Right? If "folios" list is empty, the "from" list is left unmodified. So we will reach "goto again" and retry this ops again and again. This causes soft-lockup in my test env. [ 635.267324] watchdog: BUG: soft lockup - CPU#8 stuck for 26s! [bash:1031] [ 635.277957] Kernel panic - not syncing: softlockup: hung tasks [ 635.279519] CPU: 8 PID: 1031 Comm: bash Tainted: G L 6.10.0-rc5-00327-g47fd2329f867 #45 [ 635.279796] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 635.279796] Call Trace: [ 635.279796] <IRQ> [ 635.279796] panic+0x326/0x350 [ 635.280827] watchdog_timer_fn+0x226/0x270 [ 635.280827] ? __pfx_watchdog_timer_fn+0x10/0x10 [ 635.280827] __hrtimer_run_queues+0x1a8/0x360 [ 635.280827] hrtimer_interrupt+0xfe/0x240 [ 635.280827] __sysvec_apic_timer_interrupt+0x71/0x1f0 [ 635.280827] sysvec_apic_timer_interrupt+0x6a/0x80 [ 635.280827] </IRQ> [ 635.280827] <TASK> [ 635.282706] asm_sysvec_apic_timer_interrupt+0x1a/0x20 [ 635.282928] RIP: 0010:migrate_pages_batch+0x780/0xd50 [ 635.282928] Code: 6c 24 28 41 89 46 0c 48 8b 44 24 70 03 54 24 04 c7 44 24 58 f4 ff ff ff 41 01 56 04 48 39 c8 0f 84 d0 03 00 00 e8 d0 5c fa ff <c7> 44 24 54 00 00 00 00 48 8b 94 24 80 00 00 00 48 8b 02 48 8d 6a [ 635.282928] RSP: 0018:ffffa76f88e57a00 EFLAGS: 00000246 [ 635.282928] RAX: 0000000000000000 RBX: ffffa76f88e57c50 RCX: ffffa76f88e57c60 [ 635.284331] RDX: ffffa76f88e57b78 RSI: ffffffffa7d1eb10 RDI: ffffa76f88e57b78 [ 635.284331] RBP: ffffdbcfc5000000 R08: 0000000000000000 R09: 0000000000000002 [ 635.284331] R10: 0000000000000007 R11: 0000000000000000 R12: ffffa76f88e57b70 [ 635.285800] R13: ffffa76f88e57ba8 R14: ffffa76f88e57bd0 R15: ffffa76f88e57b70 [ 635.285800] ? __pfx_alloc_migration_target+0x10/0x10 [ 635.285800] ? __pfx_alloc_migration_target+0x10/0x10 [ 635.286824] migrate_pages+0xaa7/0xd70 [ 635.286824] ? __pfx_alloc_migration_target+0x10/0x10 [ 635.287433] ? folio_lruvec_lock_irq+0x6a/0xf0 [ 635.287433] ? folio_isolate_lru+0x198/0x2a0 [ 635.287433] do_migrate_range+0x194/0x740 [ 635.287433] offline_pages+0x4ab/0x6e0 [ 635.288614] memory_subsys_offline+0x9e/0x1d0 [ 635.288803] ? _raw_spin_unlock_irqrestore+0x2c/0x50 [ 635.289119] device_offline+0xe2/0x110 [ 635.289119] state_store+0x6d/0xc0 [ 635.289119] kernfs_fop_write_iter+0x12c/0x1d0 [ 635.290093] vfs_write+0x380/0x540 [ 635.290093] ksys_write+0x64/0xe0 [ 635.290551] do_syscall_64+0xb9/0x1d0 [ 635.290551] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 635.290551] RIP: 0033:0x7f99f5514887 [ 635.290551] Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 [ 635.291480] RSP: 002b:00007ffe05712888 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 635.291480] RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007f99f5514887 [ 635.292980] RDX: 0000000000000008 RSI: 000055c97b961e10 RDI: 0000000000000001 [ 635.292980] RBP: 000055c97b961e10 R08: 00007f99f55d1460 R09: 000000007fffffff [ 635.292980] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000008 [ 635.292980] R13: 00007f99f561b780 R14: 00007f99f5617600 R15: 00007f99f5616a00 [ 635.294155] </TASK> [ 635.294155] Kernel Offset: 0x26a00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 635.294155] ---[ end Kernel panic - not syncing: softlockup: hung tasks ]--- Thanks. .
