Re: [linux-next:master] [loop] d908729e74: stress-ng.umount.ops_per_sec 100.0% regression

hi, Tetsuo Handa,

On Wed, Jul 15, 2026 at 11:25:38PM +0900, Tetsuo Handa wrote:
> On 2026/07/15 22:55, kernel test robot wrote:
> > 
> > hi, Tetsuo Handa,
> > 
> > this report is just FYI.
> > we understand d908729e74 is an experimental patch, and it seems there are lots
> > of print while running stress-ng.umount tests (one dmesg is attached)
> > 
> > [   59.370110][T10457] do_umount: task=stress-ng-umoun[10457] propagate_mount_busy()!=0
> > [   59.394831][T10476] do_umount: task=stress-ng-umoun[10476] propagate_mount_busy()!=0
> > [   59.404989][T10477] do_umount: task=stress-ng-umoun[10477] propagate_mount_busy()!=0
> > [   59.414578][T10473] do_umount: task=stress-ng-umoun[10473] propagate_mount_busy()!=0
> > [   59.423911][T10460] do_umount: task=stress-ng-umoun[10460] propagate_mount_busy()!=0
> > 
> > ....
> > 
> > 
> > so the very slow performance is expected?
> 
> Since printk() is a slow operation, stressing umount() operation that fail with -EBUSY
> can cause significantly slow performance. Can you try without fs/namespace.c changes?
> 

I saw v5 patch which removes fs/namespace.c changes.
we won't do manual tests upon it. instead, our bot would automatically bisect
and report if new version has any performance impacts. thanks