On Fri, Feb 28, 2014 at 12:47 PM, Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote: > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: > >> On Wed, 26 Feb 2014 13:22:16 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote: >> >>> 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 ? >> >> Yes. >> >>> > 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 >>> >> >> I'm lost. What patch are you talking about? The first hunk of what? > > The patch in this thread. > >> >> I assume we're talking about >> mm-numa-bugfix-for-last_cpupid_not_in_page_flags.patch, which I had >> queued for 3.14. I'll put it on hold until there's some clarity here. > > We don't need the complete patch, it is just the first hunk that we need > to fix the crash ie. we only need > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a7b4e31..ddc66df4 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -727,7 +727,7 @@ static inline int page_cpupid_last(struct page *page) > } > static inline void page_cpupid_reset_last(struct page *page) > { > - page->_last_cpupid = -1; > + page->_last_cpupid = -1 & LAST_CPUPID_MASK; > } > #else > static inline int page_cpupid_last(struct page *page) > > Also the issue will only happen when SPARSE_VMEMMAP is not enabled. I > will send a proper patch with updated changelog. I was hoping Liu will > get to that quickly > Thanks for sending V2. Since the ppc machine env is changed by others, I am blocking on setting up the env for re-test this patch. And not send out it quickly. Best regards, Fan > > -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>