On Tuesday 04 June 2013 20:17:02 Frank Mehnert wrote: > On Tuesday 04 June 2013 16:02:30 Michal Hocko wrote: > > On Tue 04-06-13 14:14:45, Frank Mehnert wrote: > > > On Tuesday 04 June 2013 13:58:07 Robin Holt wrote: > > > > This is probably more appropriate to be directed at the linux-mm > > > > mailing list. > > > > > > > > On Tue, Jun 04, 2013 at 09:22:10AM +0200, Frank Mehnert wrote: > > > > > Hi, > > > > > > > > > > our memory management on Linux hosts conflicts with NUMA page > > > > > migration. I assume this problem existed for a longer time but > > > > > Linux 3.8 introduced automatic NUMA page balancing which makes the > > > > > problem visible on multi-node hosts leading to kernel oopses. > > > > > > > > > > NUMA page migration means that the physical address of a page > > > > > changes. This is fatal if the application assumes that this never > > > > > happens for that page as it was supposed to be pinned. > > > > > > > > > > We have two kind of pinned memory: > > > > > > > > > > A) 1. allocate memory in userland with mmap() > > > > > > > > > > 2. madvise(MADV_DONTFORK) > > > > > 3. pin with get_user_pages(). > > > > > 4. flush dcache_page() > > > > > 5. vm_flags |= (VM_DONTCOPY | VM_LOCKED) > > > > > > > > > > (resulting flags are VM_MIXEDMAP | VM_DONTDUMP | > > > > > VM_DONTEXPAND > > > > > > > > > > VM_DONTCOPY | VM_LOCKED | 0xff) > > > > > > > > I don't think this type of allocation should be affected. The > > > > get_user_pages() call should elevate the pages reference count which > > > > should prevent migration from completing. I would, however, wait for > > > > a more definitive answer. > > > > > > Thanks Robin! Actually case B) is more important for us so I'm waiting > > > for more feedback :) > > > > The manual node migration code seems to be OK in case B as well because > > Reserved are skipped (check check_pte_range called from down the > > do_migrate_pages path). > > > > Maybe auto-numa code is missing this check assuming that it cannot > > encounter reserved pages. > > > > migrate_misplaced_page relies on numamigrate_isolate_page which relies > > on isolate_lru_page and that one expects a LRU page. Is your Reserved > > page on the LRU list? That would be a bit unexpected. > > I will check this. I tested this now. When the Oops happens, PageLRU() of the corresponding page struct is NOT set! I've patched the kernel to find that out. This is case B from my original mail (alloc_pages(), SetPageReserved(), vm_mmap(), vm_insert_page(), vm_flags |= (VM_DONTEXPAND | VM_DONTDUMP)) and PageLRU() was clear after vm_insert_page(). Example of such an oops (the present bits of PMD and PTE are clear): BUG: unable to handle kernel paging request at 00007ff493c7eff8 IP: [<ffffffffa039e17f>] 0xffffffffa039e17e PGD 201b068067 PUD 381c082067 PMD 20063d2166 PTE 8000002005da9166 Oops: 0000 [#1] SMP Modules linked in: pci_stub vboxpci(OF) vboxnetadp(OF) vboxnetflt(OF) vboxdrv(OF) md4 nls_utf8 cifs fscache vesafb kvm_amd kvm psmouse serio_raw microcode ib_mthca ib_mad ib_core amd64_edac_mod edac_core k10temp edac_mce_amd joydev shpchp mac_hid lp parport i2c_nforce2 hid_generic usbhid hid mptsas mptscsih mptbase scsi_transport_sas e1000 pata_acpi pata_amd CPU 24 Pid: 2058, comm: EMT Tainted: GF O 3.8.0-23-generic #34 Sun Microsystems Sun Fire X4600 M2/Sun Fire X4600 M2 RIP: 0010:[<ffffffffa039e17f>] [<ffffffffa039e17f>] 0xffffffffa039e17e RSP: 0018:ffff88381bac1968 EFLAGS: 00010202 RAX: 00007ff493c7eff8 RBX: ffff88381bac1998 RCX: 0000000000000000 RDX: 0000000000000ff8 RSI: 0000000000000000 RDI: ffff88381bac1a18 RBP: ffff88381bac1988 R08: ffffc90029981000 R09: ffffc9002999c000 R10: ffff88381bac1998 R11: ffffffffa037aee0 R12: ffffc9002999c000 R13: ffffffffa002f98d R14: ffffffffa002f98d R15: ffffc9002999c000 FS: 00007ff4f59b7700(0000) GS:ffff883827c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007ff493c7eff8 CR3: 000000201b06f000 CR4: 00000000000007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process EMT (pid: 2058, threadinfo ffff88381bac0000, task ffff88381b840000) Stack: 0000000000000000 ffff88381bac1a60 ffff88381bac1ab8 ffffffffa002f98d ffff88381bac1a28 ffffffffa039e5bd ffffffffa002f98d 0000000000000000 0000000000000000 0000000000000000 00007ff493c7e000 00007ff493c7eff8 Any more ideas? I'm happy to perform more tests. Thanks, Frank > In the meantime I verified that my testcase does not fail if I pass > 'numa_balancing=false' to the kernel, so it's definitely a NUMA balancing > problem. > > I also did 'get_page()' on all pages of method B but the testcase so this > didn't help. > > Frank -- Dr.-Ing. Frank Mehnert | Software Development Director, VirtualBox ORACLE Deutschland B.V. & Co. KG | Werkstr. 24 | 71384 Weinstadt, Germany Hauptverwaltung: Riesstr. 25, D-80992 München Registergericht: Amtsgericht München, HRA 95603 Geschäftsführer: Jürgen Kunz Komplementärin: ORACLE Deutschland Verwaltung B.V. Hertogswetering 163/167, 3543 AS Utrecht, Niederlande Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697 Geschäftsführer: Alexander van der Ven, Astrid Kepper, Val Maher
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