Memory leak in 6.18

[Harry Yoo]

On Sun, Nov 09, 2025 at 11:36:26PM +0100, Tytus Rogalewski wrote:
> Hi guys,
> 
> Been using 6.18 kernel and i have noticed that there is some memory leak.
> Currently mapple_node takes 86GB when server does not do much.
> I do not see that issue on 6.17 kernel at all.

Hi Tytus, thanks for the report!

Could you please boot your machine with kernel boot
parameter slab_debug=U [1] and run

$ cat /sys/kernel/debug/slab/maple_node/alloc_traces

and

$ cat /sys/kernel/debug/slab/maple_node/free_traces

?

> Total 1000 GB memory
> ASRockRack GENOA2D24G-2L
> 2x AMD EPYC 9654 96-Core Processor
> Running Proxmox 9
> 
>  Active / Total Objects (% used)    : 472110239 / 472257124 (100.0%)
>  Active / Total Slabs (% used)      : 7385489 / 7385489 (100.0%)
>  Active / Total Caches (% used)     : 164 / 231 (71.0%)
>  Active / Total Size (% used)       : 95486861.00K / 95528053.72K (100.0%)
>  Minimum / Average / Maximum Object : 0.01K / 0.20K / 8.06K
> 
>   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
> 345907216 345897683  99%    0.25K 5404801       64  86476816K maple_node
> 120873408 120841337  99%    0.06K 1888647       64   7554588K dmaengine-unmap-2
> 224256 223324  99%    0.01K    438      512      1752K kmalloc-8
> 224040 224040 100%    0.13K   3734       60     29872K kernfs_node_cache
> 196608 196608 100%    0.01K    384      512      1536K kmalloc-cg-8
> 196160 166455  84%    0.50K   3065       64     98080K kmalloc-512

Not sure if this is because of sheaves or maple tree changes.
Let's see what's in the alloc & free traces.

Or it would be great if you could build the kernel and perform
git bisection [2] and give us what is the first bad commit.

Thanks!

[1] https://docs.kernel.org/next/admin-guide/mm/slab.html 
[2] https://git-scm.com/docs/git-bisect

-- 
Cheers,
Harry / Hyeonggon