Memory leak in 6.18

[Harry Yoo]

On Mon, Nov 10, 2025 at 03:04:02PM +0900, Harry Yoo wrote:
> 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.

Cc'ing linux-mm at kvack.org properly as I modified the address by mistake.

> 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