| Message ID | 1612422084-30429-1-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm/page_alloc: Fix pageblock_order with HUGETLB_PAGE_SIZE_VARIABLE | expand |
On 2/4/21 12:31 PM, Anshuman Khandual wrote: > The following warning gets triggered while trying to boot a 64K page size > without THP config kernel on arm64 platform. > > WARNING: CPU: 5 PID: 124 at mm/vmstat.c:1080 __fragmentation_index+0xa4/0xc0 > Modules linked in: > CPU: 5 PID: 124 Comm: kswapd0 Not tainted 5.11.0-rc6-00004-ga0ea7d62002 #159 > Hardware name: linux,dummy-virt (DT) > [ 8.810673] pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--) > [ 8.811732] pc : __fragmentation_index+0xa4/0xc0 > [ 8.812555] lr : fragmentation_index+0xf8/0x138 > [ 8.813360] sp : ffff0000864079b0 > [ 8.813958] x29: ffff0000864079b0 x28: 0000000000000372 > [ 8.814901] x27: 0000000000007682 x26: ffff8000135b3948 > [ 8.815847] x25: 1fffe00010c80f48 x24: 0000000000000000 > [ 8.816805] x23: 0000000000000000 x22: 000000000000000d > [ 8.817764] x21: 0000000000000030 x20: ffff0005ffcb4d58 > [ 8.818712] x19: 000000000000000b x18: 0000000000000000 > [ 8.819656] x17: 0000000000000000 x16: 0000000000000000 > [ 8.820613] x15: 0000000000000000 x14: ffff8000114c6258 > [ 8.821560] x13: ffff6000bff969ba x12: 1fffe000bff969b9 > [ 8.822514] x11: 1fffe000bff969b9 x10: ffff6000bff969b9 > [ 8.823461] x9 : dfff800000000000 x8 : ffff0005ffcb4dcf > [ 8.824415] x7 : 0000000000000001 x6 : 0000000041b58ab3 > [ 8.825359] x5 : ffff600010c80f48 x4 : dfff800000000000 > [ 8.826313] x3 : ffff8000102be670 x2 : 0000000000000007 > [ 8.827259] x1 : ffff000086407a60 x0 : 000000000000000d > [ 8.828218] Call trace: > [ 8.828667] __fragmentation_index+0xa4/0xc0 > [ 8.829436] fragmentation_index+0xf8/0x138 > [ 8.830194] compaction_suitable+0x98/0xb8 > [ 8.830934] wakeup_kcompactd+0xdc/0x128 > [ 8.831640] balance_pgdat+0x71c/0x7a0 > [ 8.832327] kswapd+0x31c/0x520 > [ 8.832902] kthread+0x224/0x230 > [ 8.833491] ret_from_fork+0x10/0x30 > [ 8.834150] ---[ end trace 472836f79c15516b ]--- > > This warning comes from __fragmentation_index() when the requested order > is greater than MAX_ORDER. > > static int __fragmentation_index(unsigned int order, > struct contig_page_info *info) > { > unsigned long requested = 1UL << order; > > if (WARN_ON_ONCE(order >= MAX_ORDER)) <===== Triggered here > return 0; > > Digging it further reveals that pageblock_order has been assigned a value > which is greater than MAX_ORDER failing the above check. But why this > happened ? Because HUGETLB_PAGE_ORDER for the given config on arm64 is > greater than MAX_ORDER. > > The solution involves enabling HUGETLB_PAGE_SIZE_VARIABLE which would make > pageblock_order a variable instead of constant HUGETLB_PAGE_ORDER. But that > change alone also did not really work as pageblock_order still got assigned > as HUGETLB_PAGE_ORDER in set_pageblock_order(). HUGETLB_PAGE_ORDER needs to > be less than MAX_ORDER for its appropriateness as pageblock_order otherwise > just fallback to MAX_ORDER - 1 as before. While here it also fixes a build > problem via type casting MAX_ORDER in rmem_cma_setup(). > > This series applies in v5.11-rc6 and has been slightly tested on arm64. But > looking for some early feedbacks particularly with respect to concerns in > subscribing HUGETLB_PAGE_SIZE_VARIABLE on a platform where the hugetlb page > size is config dependent but not really a runtime variable. Even though it > appears that HUGETLB_PAGE_SIZE_VARIABLE is used only while computing the > pageblock_order, could there be other implications ? > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: linux-arm-kernel@lists.infradead.org > Cc: iommu@lists.linux-foundation.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org Probably missed some more folks, adding them here. + Michal Hocko <mhocko@kernel.org> + Vlastimil Babka <vbabka@suse.cz> + Mike Kravetz <mike.kravetz@oracle.com> + Matthew Wilcox <willy@infradead.org>
The following warning gets triggered while trying to boot a 64K page size without THP config kernel on arm64 platform. WARNING: CPU: 5 PID: 124 at mm/vmstat.c:1080 __fragmentation_index+0xa4/0xc0 Modules linked in: CPU: 5 PID: 124 Comm: kswapd0 Not tainted 5.11.0-rc6-00004-ga0ea7d62002 #159 Hardware name: linux,dummy-virt (DT) [ 8.810673] pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--) [ 8.811732] pc : __fragmentation_index+0xa4/0xc0 [ 8.812555] lr : fragmentation_index+0xf8/0x138 [ 8.813360] sp : ffff0000864079b0 [ 8.813958] x29: ffff0000864079b0 x28: 0000000000000372 [ 8.814901] x27: 0000000000007682 x26: ffff8000135b3948 [ 8.815847] x25: 1fffe00010c80f48 x24: 0000000000000000 [ 8.816805] x23: 0000000000000000 x22: 000000000000000d [ 8.817764] x21: 0000000000000030 x20: ffff0005ffcb4d58 [ 8.818712] x19: 000000000000000b x18: 0000000000000000 [ 8.819656] x17: 0000000000000000 x16: 0000000000000000 [ 8.820613] x15: 0000000000000000 x14: ffff8000114c6258 [ 8.821560] x13: ffff6000bff969ba x12: 1fffe000bff969b9 [ 8.822514] x11: 1fffe000bff969b9 x10: ffff6000bff969b9 [ 8.823461] x9 : dfff800000000000 x8 : ffff0005ffcb4dcf [ 8.824415] x7 : 0000000000000001 x6 : 0000000041b58ab3 [ 8.825359] x5 : ffff600010c80f48 x4 : dfff800000000000 [ 8.826313] x3 : ffff8000102be670 x2 : 0000000000000007 [ 8.827259] x1 : ffff000086407a60 x0 : 000000000000000d [ 8.828218] Call trace: [ 8.828667] __fragmentation_index+0xa4/0xc0 [ 8.829436] fragmentation_index+0xf8/0x138 [ 8.830194] compaction_suitable+0x98/0xb8 [ 8.830934] wakeup_kcompactd+0xdc/0x128 [ 8.831640] balance_pgdat+0x71c/0x7a0 [ 8.832327] kswapd+0x31c/0x520 [ 8.832902] kthread+0x224/0x230 [ 8.833491] ret_from_fork+0x10/0x30 [ 8.834150] ---[ end trace 472836f79c15516b ]--- This warning comes from __fragmentation_index() when the requested order is greater than MAX_ORDER. static int __fragmentation_index(unsigned int order, struct contig_page_info *info) { unsigned long requested = 1UL << order; if (WARN_ON_ONCE(order >= MAX_ORDER)) <===== Triggered here return 0; Digging it further reveals that pageblock_order has been assigned a value which is greater than MAX_ORDER failing the above check. But why this happened ? Because HUGETLB_PAGE_ORDER for the given config on arm64 is greater than MAX_ORDER. The solution involves enabling HUGETLB_PAGE_SIZE_VARIABLE which would make pageblock_order a variable instead of constant HUGETLB_PAGE_ORDER. But that change alone also did not really work as pageblock_order still got assigned as HUGETLB_PAGE_ORDER in set_pageblock_order(). HUGETLB_PAGE_ORDER needs to be less than MAX_ORDER for its appropriateness as pageblock_order otherwise just fallback to MAX_ORDER - 1 as before. While here it also fixes a build problem via type casting MAX_ORDER in rmem_cma_setup(). This series applies in v5.11-rc6 and has been slightly tested on arm64. But looking for some early feedbacks particularly with respect to concerns in subscribing HUGETLB_PAGE_SIZE_VARIABLE on a platform where the hugetlb page size is config dependent but not really a runtime variable. Even though it appears that HUGETLB_PAGE_SIZE_VARIABLE is used only while computing the pageblock_order, could there be other implications ? Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-arm-kernel@lists.infradead.org Cc: iommu@lists.linux-foundation.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Anshuman Khandual (3): mm/page_alloc: Fix pageblock_order when HUGETLB_PAGE_ORDER >= MAX_ORDER arm64/hugetlb: Enable HUGETLB_PAGE_SIZE_VARIABLE dma-contiguous: Type cast MAX_ORDER as unsigned int arch/arm64/Kconfig | 4 ++++ kernel/dma/contiguous.c | 2 +- mm/page_alloc.c | 2 +- 3 files changed, 6 insertions(+), 2 deletions(-)