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 <sudar...@codeaurora.org>
> Cc: Catalin Marinas <catalin.mari...@arm.com>
> Cc: Will Deacon <w...@kernel.org>
> Cc: Anshuman Khandual <anshuman.khand...@arm.com>
> Cc: Mark Rutland <mark.rutl...@arm.com>
> Cc: Logan Gunthorpe <log...@deltatee.com>
> Cc: David Hildenbrand <da...@redhat.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Steven Price <steven.pr...@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.
