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When kmalloc_node() is called without __GFP_THISNODE and the target node
lacks sufficient memory, SLUB allocates a folio from a different node
other than the requested node, instead of taking a partial slab from it.
However, since the allocated folio does not belong to the requested
node, on the following allocation it is deactivated and added to the
partial slab list of the node it belongs to.
This behavior can result in excessive memory usage when the requested
node has insufficient memory, as SLUB will repeatedly allocate folios
from other nodes without reusing the previously allocated ones.
To prevent memory wastage, when a preferred node is indicated (not
NUMA_NO_NODE) but without a prior __GFP_THISNODE constraint:
1) try to get a partial slab from target node only by having
__GFP_THISNODE in pc.flags for get_partial()
2) if 1) failed, try to allocate a new slab from target node with
GFP_NOWAIT | __GFP_THISNODE opportunistically.
3) if 2) failed, retry with original gfpflags which will allow
get_partial() try partial lists of other nodes before potentially
allocating new page from other nodes
Without a preferred node, or with __GFP_THISNODE constraint, the
behavior remains unchanged.
On qemu with 4 numa nodes and each numa has 1G memory. Write a test ko
to call kmalloc_node(196, GFP_KERNEL, 3) for (4 * 1024 + 4) * 1024 times.
cat /proc/slabinfo shows:
kmalloc-256 4200530 13519712 256 32 2 : tunables..
after this patch,
cat /proc/slabinfo shows:
kmalloc-256 4200558 4200768 256 32 2 : tunables..
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
9198ffbd2b