Re: [PATCH v2 1/7] drm/xe: Adjust long-running workload timeslices to reasonable values

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Dec 15, 2025 at 11:08:21AM +0100, Thomas Hellström wrote:
> On Fri, 2025-12-12 at 10:28 -0800, Matthew Brost wrote:
> > A 10ms timeslice for long-running workloads is far too long and
> > causes
> > significant jitter in benchmarks when the system is shared. Adjust
> > the
> > value to 5ms for preempt-fencing VMs, as the resume step there is
> > quite
> > costly as memory is moved around, and set it to zero for pagefault
> > VMs,
> > since switching back to pagefault mode after dma-fence mode is
> > relatively fast.
> > 
> > Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel
> > GPUs")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> 
> Please add a comment in the commit message explaining why the type was
> changed.
> 

Will do. I noticed s64 type which makes no sense at all when working on
this series, so fixed that part up too.

Matt

> Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> 
> > ---
> >  drivers/gpu/drm/xe/xe_vm.c       | 5 ++++-
> >  drivers/gpu/drm/xe/xe_vm_types.h | 2 +-
> >  2 files changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> > index c2012d20faa6..4648f8a458cf 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.c
> > +++ b/drivers/gpu/drm/xe/xe_vm.c
> > @@ -1508,7 +1508,10 @@ struct xe_vm *xe_vm_create(struct xe_device
> > *xe, u32 flags, struct xe_file *xef)
> >  	INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
> >  
> >  	INIT_LIST_HEAD(&vm->preempt.exec_queues);
> > -	vm->preempt.min_run_period_ms = 10;	/* FIXME: Wire up to
> > uAPI */
> > +	if (flags & XE_VM_FLAG_FAULT_MODE)
> > +		vm->preempt.min_run_period_ms = 0;
> > +	else
> > +		vm->preempt.min_run_period_ms = 5;
> >  
> >  	for_each_tile(tile, xe, id)
> >  		xe_range_fence_tree_init(&vm->rftree[id]);
> > diff --git a/drivers/gpu/drm/xe/xe_vm_types.h
> > b/drivers/gpu/drm/xe/xe_vm_types.h
> > index 3bf912bfbdcc..18bad1dd08e6 100644
> > --- a/drivers/gpu/drm/xe/xe_vm_types.h
> > +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> > @@ -263,7 +263,7 @@ struct xe_vm {
> >  		 * @min_run_period_ms: The minimum run period before
> > preempting
> >  		 * an engine again
> >  		 */
> > -		s64 min_run_period_ms;
> > +		unsigned int min_run_period_ms;
> >  		/** @exec_queues: list of exec queues attached to
> > this VM */
> >  		struct list_head exec_queues;
> >  		/** @num_exec_queues: number exec queues attached to
> > this VM */
>