When section mappings are enabled, we allocate vmemmap pages from physically continuous memory of size PMD_SIZE using vmemmap_alloc_block_buf(). Section mappings are good to reduce TLB pressure. But when system is highly fragmented and memory blocks are being hot-added at runtime, its possible that such physically continuous memory allocations can fail. Rather than failing the memory hot-add procedure, add a fallback option to allocate vmemmap pages from discontinuous pages using vmemmap_populate_basepages().
Signed-off-by: Sudarshan Rajagopalan <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> Cc: Anshuman Khandual <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Logan Gunthorpe <[email protected]> Cc: David Hildenbrand <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Steven Price <[email protected]> --- arch/arm64/mm/mmu.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 75df62f..9edbbb8 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1121,8 +1121,18 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, void *p = NULL; p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); - if (!p) - return -ENOMEM; + if (!p) { + if (altmap) + return -ENOMEM; /* no fallback */ + + /* + * fallback allocating with virtually + * contiguous memory for this section + */ + if (vmemmap_populate_basepages(addr, next, node, NULL)) + return -ENOMEM; + continue; + } pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL)); } else -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
