[PATCH v6 12/12] drm/xe: Increase the XE_PL_TT watermark

[Thomas Hellström]

On Wed, 2024-08-07 at 23:44 +0000, Matthew Brost wrote:
> On Wed, Jul 03, 2024 at 05:38:13PM +0200, Thomas Hellström wrote:
> > The XE_PL_TT watermark was set to 50% of system memory.
> > The idea behind that was unclear since the net effect is that
> > TT memory will be evicted to TTM_PL_SYSTEM memory if that
> > watermark is exceeded, requiring PPGTT rebinds and dma
> > remapping. But there is no similar watermark for TTM_PL_SYSTEM
> > memory.
> > 
> > The TTM functionality that tries to swap out system memory to
> > shmem objects if a 50% limit of total system memory is reached
> > is orthogonal to this, and with the shrinker added, it's no
> > longer in effect.
> > 
> > Replace the 50% TTM_PL_TT limit with a 100% limit, in effect
> > allowing all graphics memory to be bound to the device unless it
> > has been swapped out by the shrinker.
> > 
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> 
> Reviewed-by: Matthew Brost <matthew.brost at intel.com>

Thanks for reviewing!
/Thomas


> 
> > ---
> >  drivers/gpu/drm/xe/xe_ttm_sys_mgr.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> > b/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> > index 9844a8edbfe1..d38b91872da3 100644
> > --- a/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> > +++ b/drivers/gpu/drm/xe/xe_ttm_sys_mgr.c
> > @@ -108,9 +108,8 @@ int xe_ttm_sys_mgr_init(struct xe_device *xe)
> >  	u64 gtt_size;
> >  
> >  	si_meminfo(&si);
> > +	/* Potentially restrict amount of TT memory here. */
> >  	gtt_size = (u64)si.totalram * si.mem_unit;
> > -	/* TTM limits allocation of all TTM devices by 50% of
> > system memory */
> > -	gtt_size /= 2;
> >  
> >  	man->use_tt = true;
> >  	man->func = &xe_ttm_sys_mgr_func;
> > -- 
> > 2.44.0
> >