> Eric Dumazet reported a strange numa spreading info in [1], and found
> commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings") introduced
> this issue [2].
>
> Dig into the difference before and after this patch, page allocation has
> some difference:
>
> before:
> alloc_large_system_hash
> __vmalloc
> __vmalloc_node(..., NUMA_NO_NODE, ...)
> __vmalloc_node_range
> __vmalloc_area_node
> alloc_page /* because NUMA_NO_NODE, so choose alloc_page branch */
> alloc_pages_current
> alloc_page_interleave /* can be proved by print policy mode */
>
> after:
> alloc_large_system_hash
> __vmalloc
> __vmalloc_node(..., NUMA_NO_NODE, ...)
> __vmalloc_node_range
> __vmalloc_area_node
> alloc_pages_node /* choose nid by nuam_mem_id() */
> __alloc_pages_node(nid, ....)
>
> So after commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings"),
> it will allocate memory in current node instead of interleaving allocate
> memory.
>
> [1]
> https://lore.kernel.org/linux-mm/CANn89iL6AAyWhfxdHO+jaT075iOa3XcYn9k6JJc7JR2XYn6k_Q@xxxxxxxxxxxxxx/
>
> [2]
> https://lore.kernel.org/linux-mm/CANn89iLofTR=AK-QOZY87RdUZENCZUT4O6a0hvhu3_EwRMerOg@xxxxxxxxxxxxxx/
>
> Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
> Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx>
> ---
> mm/vmalloc.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index d77830ff604c..87552a4018aa 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2816,6 +2816,8 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> unsigned int order, unsigned int nr_pages, struct page **pages)
> {
> unsigned int nr_allocated = 0;
> + struct page *page;
> + int i;
>
> /*
> * For order-0 pages we make use of bulk allocator, if
> @@ -2823,7 +2825,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> * to fails, fallback to a single page allocator that is
> * more permissive.
> */
> - if (!order) {
> + if (!order && nid != NUMA_NO_NODE) {
> while (nr_allocated < nr_pages) {
> unsigned int nr, nr_pages_request;
>
> @@ -2848,7 +2850,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> if (nr != nr_pages_request)
> break;
> }
> - } else
> + } else if (order)
> /*
> * Compound pages required for remap_vmalloc_page if
> * high-order pages.
> @@ -2856,11 +2858,13 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> gfp |= __GFP_COMP;
>
> /* High-order pages or fallback path if "bulk" fails. */
> - while (nr_allocated < nr_pages) {
> - struct page *page;
> - int i;
>
> - page = alloc_pages_node(nid, gfp, order);
> + page = NULL;
>
Why do you need to set page to NULL here?
--
Vlad Rezki
