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Subject[PATCH v2 1/2] mm/vmalloc: fix numa spreading for large hash tables
Date
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@mail.gmail.com/

[2]
https://lore.kernel.org/linux-mm/CANn89iLofTR=AK-QOZY87RdUZENCZUT4O6a0hvhu3_EwRMerOg@mail.gmail.com/

Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
---
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;
+ while (nr_allocated < nr_pages) {
+ if (nid == NUMA_NO_NODE)
+ page = alloc_pages(gfp, order);
+ else
+ page = alloc_pages_node(nid, gfp, order);
if (unlikely(!page))
break;

--
2.25.1
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