On 11/28/21 03:18, Maxim Levitsky wrote:
>
> dmesg prints this:
>
> HugeTLB: allocating 64 of page size 1.00 GiB failed. Only allocated 0 hugepages
>
> Huge pages were allocated on kernel command line (1/2 of 128GB system):
>
> 'default_hugepagesz=1G hugepagesz=1G hugepages=64'
>
> This is 3970X and no real support/need for NUMA, thus only fake NUMA node 0 is present.
>
> Reverting the commit helps.
>
> New syntax also works ( hugepages=0:64 )
>
> I can test any patches for this bug.
Argh! I think preallocation of gigantic pages on all systems with only
a single node is broken. The issue is at the beginning of
__alloc_bootmem_huge_page:
int __alloc_bootmem_huge_page(struct hstate *h, int nid)
{
struct huge_bootmem_page *m = NULL; /* initialize for clang */
int nr_nodes, node;
if (nid >= nr_online_nodes)
return 0;
Without using the node specific syntax, nid == NUMA_NO_NODE == -1. For the
comparison, nid will be converted to an unsigned into to match nr_online_nodes
so we will immediately return 0 instead of doing the allocations.
Zhenguo Yao,
Can you verify and perhaps put together a patch?does
>
> Also unrelated, is there any progress on allocating 1GB pages on demand so that I could
> allocate them only when I run a VM?
That should be possible. Such support was added back in 2014 with commit
944d9fec8d7a "hugetlb: add support for gigantic page allocation at runtime".
>
> i don't mind having these pages to be marked as to be used for userspace only,
> since as far as I remember its the kernel usage that makes some page unmoveable.
>
Of course, finding 1GB of contiguous space for a gigantic page is often
difficult at runtime. So, allocations are likely to fail the longer the
system is up and running and fragmentation increases.
> Last time (many years ago) I tried to create a zone with only userspace pages
> (I don't remember what options I used) but it didn't work.
Not too long ago, support was added to use CMA for gigantic page allocation.
See commit cf11e85fc08c "mm: hugetlb: optionally allocate gigantic hugepages
using cma". This sounds like something you might want to try.
--
Mike Kravetz
>
> Is there a way to debug what is causing unmoveable pages and doesn't let
> /proc/sys/vm/nr_hugepages work (I tried it today and as usual the number
> it can allocate steadly decreases over time).
