在 2025/3/3 19:47, David Hildenbrand 写道:
On 03.03.25 12:23, Jinjiang Tu wrote:
在 2025/3/3 19:16, Jinjiang Tu 写道:
在 2025/3/3 18:25, David Hildenbrand 写道:
On 03.03.25 07:09, Jinjiang Tu wrote:
In dissolve_free_huge_page(), free huge pages are dissolved without
adjusting surplus count. However, free huge pages may be accounted as
surplus pages, and will lead to wrong surplus count.
Steps to reproduce:
1) create 64 huge pages for node1
2) run a program to reserve (don't consume) all the huge pages
3) echo 0 > nr_huge_pages for node1. After this step, free huge
pages in
Node1 are surplus.
4) create 80 huge pages for node0
5) offline memory of node1 and kill the program in step 2)
Can you elaborate the "offline memory" part? How much are you
offlining (the complete node vs a single memory block?)
I reproduce this issue on qemu. The memory onlining and offlining
operations are:
1）Node1 is memory-less at first. Hot-add memory to node1 by executing
the two commands in qemu monitor
object_add memory-backend-ram,id=mem1,size=1G
device_add pc-dimm,id=dimm1,memdev=mem1,node=1
2）online one memory block of Node1 with：
echo online_movable > /sys/devices/system/node/node1/memoryX/state
3) offline the memory block of Node1 with：
echo offline > /sys/devices/system/node/node1/memoryX/state
The memory range to offline contains the free surplus huge pages created
in step1) ~ step3)
Okay, that makes it a lot clearer. Can you make that clearer in the
patch description?
Sure, I will send a v2 patch later.
The problem appears when memory offlining stumbles over a free hugetlb
folio. We'll call
dissolve_free_hugetlb_folios()->dissolve_free_hugetlb_folio() to
dissolve it, but don't adjust accounting with surplus pages properly.
I'll note that there is another dissolve_free_hugetlb_folio() caller
in the memory-failure path that might similarly be affected.
