Messages in this thread | | | Subject | Re: [PATCH v3] arm64/mm: add fallback option to allocate virtually contiguous memory | From | Anshuman Khandual <> | Date | Tue, 6 Oct 2020 09:06:20 +0530 |
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On 10/02/2020 01:46 AM, Sudarshan Rajagopalan wrote: > 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 <sudaraja@codeaurora.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Logan Gunthorpe <logang@deltatee.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Steven Price <steven.price@arm.com> > --- > arch/arm64/mm/mmu.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 75df62f..11f8639 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1121,8 +1121,15 @@ 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) { > + /* > + * fallback allocating with virtually > + * contiguous memory for this section > + */
Mapping is always virtually contiguous with or without huge pages. Please drop this comment here, as it's obvious.
> + if (vmemmap_populate_basepages(addr, next, node, NULL)) > + return -ENOMEM;
Please send in the 'altmap' instead of NULL for allocation from device memory if and when requested.
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