On Sat, Oct 26, 2013 at 02:11:48PM +0200, Ingo Molnar wrote: > > * Mel Gorman <mgorman@xxxxxxx> wrote: > > > On Mon, Oct 07, 2013 at 11:28:38AM +0100, Mel Gorman wrote: > > > This series has roughly the same goals as previous versions despite the > > > size. It reduces overhead of automatic balancing through scan rate reduction > > > and the avoidance of TLB flushes. It selects a preferred node and moves tasks > > > towards their memory as well as moving memory toward their task. It handles > > > shared pages and groups related tasks together. Some problems such as shared > > > page interleaving and properly dealing with processes that are larger than > > > a node are being deferred. This version should be ready for wider testing > > > in -tip. > > > > > > > Hi Ingo, > > > > Off-list we talked with Peter about the fact that automatic NUMA > > balancing as merged in 3.10, 3.11 and 3.12 shortly may corrupt > > userspace memory. There is one LKML report on this that I'm aware of -- > > https://lkml.org/lkml/2013/7/31/647 which I prompt forgot to follow up > > properly on . The user-visible effect is that pages get filled with zeros > > with results such as null pointer exceptions in JVMs. It is fairly difficult > > to trigger but it became much easier to trigger during the development of > > the series "Basic scheduler support for automatic NUMA balancing" which > > is how it was discovered and finally fixed. > > > > In that series I tagged patches 2-9 for -stable as these patches addressed > > the problem for me. I did not call it out as clearly as I should have > > and did not realise the cc: stable tags were stripped. Worse, as it was > > close to the release and the bug is relatively old I was ok with waiting > > until 3.12 came out and then treat it as a -stable backport. It has been > > highlighted that this is the wrong attitude and we should consider merging > > the fixes now and backporting to -stable sooner rather than later. > > > > The most important patches are > > > > mm: Wait for THP migrations to complete during NUMA hinting fault > > mm: Prevent parallel splits during THP migration > > mm: Close races between THP migration and PMD numa clearing > > > > but on their own they will cause conflicts with tricky fixups and -stable > > would differ from mainline in annoying ways. Patches 2-9 have been heavily > > tested in isolation so I'm reasonably confident they fix the problem and are > > -stable material. While strictly speaking not all the patches are required > > for the fix, the -stable kernels would then be directly comparable with > > 3.13 when the full NUMA balancing series is applied. If I rework them at > > this point then I'll also have to retest delaying things until next week. > > > > Please consider queueing patches 2-9 for 3.12 via -urgent if it is > > not too late and preserve the cc: stable tags so Greg will pick > > them up automatically. > > Would be nice if you gave me all the specific SHA1 tags of > sched/core that are required for the fix. We can certainly > use a range to make it all safer to apply. > Of course. The range of the relevant commits in tip/sched/core is ca4be374c5c0ab3d8b84fb2861d663216281e6ac..778ec5247bb79815af12434980164334fb94cc9e 904f64a376e663cd459fb7aec4f12e14c39c24b6 mm: numa: Document automatic NUMA balancing sysctls 1d649bccc8c1370e402b85e1d345ad24f3f0d1b5 sched, numa: Comment fixlets f961cab8d55d55d6abc0df08ce2abec8ab56f2c8 mm: numa: Do not account for a hinting fault if we raced 6f2a15fc1df62af3ba3be327877b7e53cb16e878 mm: Wait for THP migrations to complete during NUMA hinting faults 4ee547f994c633f2607d222e2c6385b6fe5f07d8 mm: Prevent parallel splits during THP migration dd83227f0d93fb37d7621a24e8465b13b437faa6 mm: numa: Sanitize task_numa_fault() callsites efeeacf7b94babff85da7e468fc5450fdfab0900 mm: Close races between THP migration and PMD numa clearing 778ec5247bb79815af12434980164334fb94cc9e mm: Account for a THP NUMA hinting update as one PTE update Thanks. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>