On Wed, Jul 23, 2014 at 03:28:09PM -0700, David Rientjes wrote: > > My debug code shows that certain code paths are still allowing > > ALLOC_CPUSET to get pulled off the alloc_flags with the patch, but > > monitoring the memory usage shows that we're staying on node, aside from > > some very small allocations, which may be other types of allocations that > > are not necessarly confined to a cpuset. Need a bit more research to > > confirm that. > > > > ALLOC_CPUSET should get stripped for the cases outlined in > __cpuset_node_allowed_softwall(), specifically for GFP_ATOMIC which does > not have __GFP_WAIT set. Makes sense. I knew my patch was probably the wrong way to fix this, but it did serve my purpose :) > > So, my question ends up being, why do we wipe out ___GFP_WAIT when > > defrag is off? I'll trust that there is good reason to do that, but, if > > so, is the behavior that I'm seeing expected? > > > > The intention is to avoid memory compaction (and direct reclaim), > obviously, which does not run when __GFP_WAIT is not set. But you're > exactly right that this abuses the allocflags conversion that allows > ALLOC_CPUSET to get cleared because it is using the aforementioned > GFP_ATOMIC exception for cpuset allocation. > > We can't use PF_MEMALLOC or TIF_MEMDIE for hugepage allocation because it > affects the allowed watermarks and nothing else prevents memory compaction > or direct reclaim from running in the page allocator slowpath. > > So it looks like a modification to the page allocator is needed, see > below. Looks good to me. Fixes the problem without affecting any of the other intended functionality. > It's also been a long-standing issue that cpusets and mempolicies are > ignored by khugepaged that allows memory to be migrated remotely to nodes > that are not allowed by a cpuset's mems or a mempolicy's nodemask. Even > with this issue fixed, you may find that some memory is migrated remotely, > although it may be negligible, by khugepaged. A bit here and there is manageable. There is, of course, some work to be done there, but for now we're mainly concerned with a job that's supposed to be confined to a cpuset spilling out and soaking up all the memory on a machine. Thanks for the help, David. Much appreciated! - Alex -- 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>