Handling NUMA page migration

From: Frank Mehnert
Date: Tue Jun 04 2013 - 03:22:20 EST


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 |

B) 1. allocate memory with alloc_pages()
2. SetPageReserved()
3. vm_mmap() to allocate a userspace mapping
4. vm_insert_page()
5. vm_flags |= (VM_DONTEXPAND | VM_DONTDUMP)
(resulting flags are VM_MIXEDMAP | VM_DONTDUMP | VM_DONTEXPAND | 0xff)

At least the memory allocated like B) is affected by automatic NUMA page
migration. I'm not sure about A).

1. How can I prevent automatic NUMA page migration on this memory?
2. Can NUMA page migration also be handled on such kind of memory without
preventing migration?


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
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/