Ohh, scratch that. The patch is bogus. I have completely missed that
vmemmap_populate_hugepages already falls back to
vmemmap_populate_basepages. I have to revisit the bug report I have
received to see what happened apart from the allocation warning. Maybe
we just want to silent that warning.
Sorry about the noise!
On Tue 11-07-17 15:42:04, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> vmemmap_populate uses huge pages if the CPU supports them which is good
> and usually what we want. vmemmap_alloc_block will use the bootmem
> allocator in the early initialization so the allocation will most likely
> succeed. This is not the case for the memory hotplug though. Such an
> allocation can easily fail under memory pressure. Especially so when the
> kernel memory is restricted with movable_node parameter.
>
> There is no real reason to fail the vmemmap_populate when
> vmemmap_populate_hugepages fails though. We can still fallback to
> vmemmap_populate_basepages and use base pages. The performance will not
> be optimal but this is much better than failing the memory hot add.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> arch/x86/mm/init_64.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 136422d7d539..e6e3c755b9cb 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1401,15 +1401,16 @@ static int __meminit vmemmap_populate_hugepages(unsigned long start,
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
> {
> struct vmem_altmap *altmap = to_vmem_altmap(start);
> - int err;
> + int err = -ENOMEM;
>
> if (boot_cpu_has(X86_FEATURE_PSE))
> err = vmemmap_populate_hugepages(start, end, node, altmap);
> else if (altmap) {
> pr_err_once("%s: no cpu support for altmap allocations\n",
> __func__);
> - err = -ENOMEM;
> - } else
> + return err;
> + }
> + if (err)
> err = vmemmap_populate_basepages(start, end, node);
> if (!err)
> sync_global_pgds(start, end - 1);
> --
> 2.11.0
>
--
Michal Hocko
SUSE Labs
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