On 10/13/2020 04:35 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().
There is a checkpatch warning here, which could be fixed while merging ?
WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per
line)
#7:
When section mappings are enabled, we allocate vmemmap pages from physically
total: 0 errors, 1 warnings, 13 lines checked
>
> Signed-off-by: Sudarshan Rajagopalan <sudar...@codeaurora.org>
> Reviewed-by: Gavin Shan <gs...@redhat.com>
> 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>
Nonetheless, this looks fine. Did not see any particular problem
while creating an experimental vmemmap with interleaving section
and base page mapping.
Reviewed-by: Anshuman Khandual <anshuman.khand...@arm.com>
> ---
> arch/arm64/mm/mmu.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 75df62fea1b6..44486fd0e883 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1121,8 +1121,11 @@ 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 (vmemmap_populate_basepages(addr, next,
> node, altmap))
> + return -ENOMEM;
> + continue;
> + }
>
> pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL));
> } else
>
