Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: > On Wed, 5 Feb 2014 09:25:46 +0800 Liu Ping Fan <qemulist@xxxxxxxxx> wrote: > >> When doing some numa tests on powerpc, I triggered an oops bug. I find >> it is caused by using page->_last_cpupid. It should be initialized as >> "-1 & LAST_CPUPID_MASK", but not "-1". Otherwise, in task_numa_fault(), >> we will miss the checking (last_cpupid == (-1 & LAST_CPUPID_MASK)). >> And finally cause an oops bug in task_numa_group(), since the online cpu is >> less than possible cpu. > > I grabbed this. I added this to the changelog: > > : PPC needs the LAST_CPUPID_NOT_IN_PAGE_FLAGS case because ppc needs to > : support a large physical address region, up to 2^46 but small section size > : (2^24). So when NR_CPUS grows up, it is easily to cause > : not-in-page-flags. > > to hopefully address Peter's observation. > > How should we proceed with this? I'm getting the impression that numa > balancing on ppc is a dead duck in 3.14, so perhaps this and > > powerpc-mm-add-new-set-flag-argument-to-pte-pmd-update-function.patch > mm-dirty-accountable-change-only-apply-to-non-prot-numa-case.patch > mm-use-ptep-pmdp_set_numa-for-updating-_page_numa-bit.patch > All these are already in 3.14 ? > are 3.15-rc1 material? > We should push the first hunk to 3.14. I will wait for Liu to redo the patch. BTW this should happen only when SPARSE_VMEMMAP is not specified. Srikar had reported the issue here http://mid.gmane.org/20140219180200.GA29257@xxxxxxxxxxxxxxxxxx #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) #define SECTIONS_WIDTH SECTIONS_SHIFT #else #define SECTIONS_WIDTH 0 #endif -aneesh -- 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>