On 3/30/24 9:23 AM, Chen Jun wrote: > 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, 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 (node != NUMA_NO_NODE) && !(gfpflags & __GFP_THISNODE) is, > 1) try to get a partial slab from target node with GFP_NOWAIT | > __GFP_THISNODE opportunistically. > 2) if 1) failed, try to allocate a new slab from target node with > GFP_NOWAIT | __GFP_THISNODE opportunistically too. > 3) if 2) failed, retry 1) and 2) with orignal gfpflags. > > when node != NUMA_NO_NODE || (gfpflags & __GFP_THISNODE), 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@xxxxxxxxxx> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Slightly reworded and added an unlikely() to one of the tests, and included in slab/for-6.10: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/commit/?h=slab/for-6.10/cleanup&id=9198ffbd2b494daae3a67cac1d59c3a2754e64cd Thanks!
