Re: [Intel-xe] [PATCH v2 08/31] drm/xe: VM LRU bulk move

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

On Tue, May 09, 2023 at 02:47:54PM +0200, Thomas Hellström wrote:
> 
> On 5/2/23 02:17, Matthew Brost wrote:
> > Use the TTM LRU bulk move for BOs tied to a VM. Update the bulk moves
> > LRU position on every exec.
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >   drivers/gpu/drm/xe/xe_bo.c       | 32 ++++++++++++++++++++++++++++----
> >   drivers/gpu/drm/xe/xe_bo.h       |  4 ++--
> >   drivers/gpu/drm/xe/xe_dma_buf.c  |  2 +-
> >   drivers/gpu/drm/xe/xe_exec.c     |  6 ++++++
> >   drivers/gpu/drm/xe/xe_vm_types.h |  3 +++
> >   5 files changed, 40 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> > index 3ab404e33fae..da99ee53e7d7 100644
> > --- a/drivers/gpu/drm/xe/xe_bo.c
> > +++ b/drivers/gpu/drm/xe/xe_bo.c
> > @@ -985,6 +985,23 @@ static void xe_gem_object_free(struct drm_gem_object *obj)
> >   	ttm_bo_put(container_of(obj, struct ttm_buffer_object, base));
> >   }
> > +static void xe_gem_object_close(struct drm_gem_object *obj,
> > +				struct drm_file *file_priv)
> > +{
> > +	struct xe_bo *bo = gem_to_xe_bo(obj);
> > +
> > +	if (bo->vm && !xe_vm_no_dma_fences(bo->vm)) {
> Is there a reason we don't use bulk moves for LR vms? Admittedly bumping LRU
> doesn't make much sense when we support user-space command buffer chaining,
> but I think we should be doing it on exec at least, no?

Maybe you could make the argument for compute VMs, the preempt worker in
that case should probably do a bulk move. I can change this if desired.

Fot a fault VM it makes no sense as the fault handler updates the LRU
for individual BOs.

> > +		struct ww_acquire_ctx ww;
> > +
> > +		XE_BUG_ON(!xe_bo_is_user(bo));
> 
> Also why can't we use this for kernel objects as well? At some point we want
> to get to evictable page-table objects? Could we do this in the
> release_notify() callback to cover all potential bos?
> 

xe_gem_object_close is a user call, right? We can't call this on kernel
BOs. This also could be outside the if statement.

Matt

> /Thomas
> 
>