Re: [Intel-gfx] [CI 1/2] drm/mm: Add an iterator to optimally walk over holes for an allocation (v4)

["Kasireddy, Vivek" <vivek.kasireddy@intel.com>]

Hi Tvrtko,

> 
> Hi Vivek,
> 
> On 27/02/2022 17:29, Vivek Kasireddy wrote:
> > This iterator relies on drm_mm_first_hole() and drm_mm_next_hole()
> > functions to identify suitable holes for an allocation of a given
> > size by efficiently traversing the rbtree associated with the given
> > allocator.
> >
> > It replaces the for loop in drm_mm_insert_node_in_range() and can
> > also be used by drm drivers to quickly identify holes of a certain
> > size within a given range.
> >
> > v2: (Tvrtko)
> > - Prepend a double underscore for the newly exported first/next_hole
> > - s/each_best_hole/each_suitable_hole/g
> > - Mask out DRM_MM_INSERT_ONCE from the mode before calling
> >    first/next_hole and elsewhere.
> >
> > v3: (Tvrtko)
> > - Reduce the number of hunks by retaining the "mode" variable name
> >
> > v4:
> > - Typo: s/__drm_mm_next_hole(.., hole/__drm_mm_next_hole(.., pos
> >
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > Acked-by: Christian König <christian.koenig@amd.com>
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> > Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> > ---
> >   drivers/gpu/drm/drm_mm.c | 32 +++++++++++++++-----------------
> >   include/drm/drm_mm.h     | 36 ++++++++++++++++++++++++++++++++++++
> >   2 files changed, 51 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> > index 8257f9d4f619..8efea548ae9f 100644
> > --- a/drivers/gpu/drm/drm_mm.c
> > +++ b/drivers/gpu/drm/drm_mm.c
> > @@ -352,10 +352,10 @@ static struct drm_mm_node *find_hole_addr(struct drm_mm
> *mm, u64 addr, u64 size)
> >   	return node;
> >   }
> >
> > -static struct drm_mm_node *
> > -first_hole(struct drm_mm *mm,
> > -	   u64 start, u64 end, u64 size,
> > -	   enum drm_mm_insert_mode mode)
> > +struct drm_mm_node *
> > +__drm_mm_first_hole(struct drm_mm *mm,
> > +		    u64 start, u64 end, u64 size,
> > +		    enum drm_mm_insert_mode mode)
> >   {
> >   	switch (mode) {
> >   	default:
> > @@ -374,6 +374,7 @@ first_hole(struct drm_mm *mm,
> >   						hole_stack);
> >   	}
> >   }
> > +EXPORT_SYMBOL(__drm_mm_first_hole);
> >
> >   /**
> >    * DECLARE_NEXT_HOLE_ADDR - macro to declare next hole functions
> > @@ -410,11 +411,11 @@ static struct drm_mm_node *name(struct drm_mm_node
> *entry, u64 size)	\
> >   DECLARE_NEXT_HOLE_ADDR(next_hole_high_addr, rb_left, rb_right)
> >   DECLARE_NEXT_HOLE_ADDR(next_hole_low_addr, rb_right, rb_left)
> >
> > -static struct drm_mm_node *
> > -next_hole(struct drm_mm *mm,
> > -	  struct drm_mm_node *node,
> > -	  u64 size,
> > -	  enum drm_mm_insert_mode mode)
> > +struct drm_mm_node *
> > +__drm_mm_next_hole(struct drm_mm *mm,
> > +		   struct drm_mm_node *node,
> > +		   u64 size,
> > +		   enum drm_mm_insert_mode mode)
> >   {
> >   	switch (mode) {
> >   	default:
> > @@ -432,6 +433,7 @@ next_hole(struct drm_mm *mm,
> >   		return &node->hole_stack == &mm->hole_stack ? NULL : node;
> >   	}
> >   }
> > +EXPORT_SYMBOL(__drm_mm_next_hole);
> >
> >   /**
> >    * drm_mm_reserve_node - insert an pre-initialized node
> > @@ -516,11 +518,11 @@ int drm_mm_insert_node_in_range(struct drm_mm * const
> mm,
> >   				u64 size, u64 alignment,
> >   				unsigned long color,
> >   				u64 range_start, u64 range_end,
> > -				enum drm_mm_insert_mode mode)
> > +				enum drm_mm_insert_mode caller_mode)
> >   {
> >   	struct drm_mm_node *hole;
> >   	u64 remainder_mask;
> > -	bool once;
> > +	enum drm_mm_insert_mode mode = caller_mode &
> ~DRM_MM_INSERT_ONCE;
> >
> >   	DRM_MM_BUG_ON(range_start > range_end);
> >
> > @@ -533,13 +535,9 @@ int drm_mm_insert_node_in_range(struct drm_mm * const
> mm,
> >   	if (alignment <= 1)
> >   		alignment = 0;
> >
> > -	once = mode & DRM_MM_INSERT_ONCE;
> > -	mode &= ~DRM_MM_INSERT_ONCE;
> > -
> >   	remainder_mask = is_power_of_2(alignment) ? alignment - 1 : 0;
> > -	for (hole = first_hole(mm, range_start, range_end, size, mode);
> > -	     hole;
> > -	     hole = once ? NULL : next_hole(mm, hole, size, mode)) {
> > +	drm_mm_for_each_suitable_hole(hole, mm, range_start, range_end,
> > +				      size, mode) {
> 
> I was doing one last read of the patch before I ask the maintainers
> where to merge it and realized - don't you need to pass in the
> caller_mode just here (not mode which has been masked out from "once")?
> Otherwise "once" mode will not be respected by the iterator.
[Kasireddy, Vivek] Right, yet another typo; it should have been caller_mode
instead of mode. Let me fix it and run it through another CI cycle.

Thanks,
Vivek
> 
> Regards,
> 
> Tvrtko
> 
> >   		u64 hole_start = __drm_mm_hole_node_start(hole);
> >   		u64 hole_end = hole_start + hole->hole_size;
> >   		u64 adj_start, adj_end;
> > diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
> > index ac33ba1b18bc..dff6db627807 100644
> > --- a/include/drm/drm_mm.h
> > +++ b/include/drm/drm_mm.h
> > @@ -400,6 +400,42 @@ static inline u64 drm_mm_hole_node_end(const struct
> drm_mm_node *hole_node)
> >   	     1 : 0; \
> >   	     pos = list_next_entry(pos, hole_stack))
> >
> > +struct drm_mm_node *
> > +__drm_mm_first_hole(struct drm_mm *mm,
> > +		    u64 start, u64 end, u64 size,
> > +		    enum drm_mm_insert_mode mode);
> > +
> > +struct drm_mm_node *
> > +__drm_mm_next_hole(struct drm_mm *mm,
> > +		   struct drm_mm_node *node,
> > +		   u64 size,
> > +		   enum drm_mm_insert_mode mode);
> > +
> > +/**
> > + * drm_mm_for_each_suitable_hole - iterator to optimally walk over all
> > + * holes that can fit an allocation of the given @size.
> > + * @pos: &drm_mm_node used internally to track progress
> > + * @mm: &drm_mm allocator to walk
> > + * @range_start: start of the allowed range for the allocation
> > + * @range_end: end of the allowed range for the allocation
> > + * @size: size of the allocation
> > + * @mode: fine-tune the allocation search
> > + *
> > + * This iterator walks over all holes suitable for the allocation of given
> > + * @size in a very efficient manner. It is implemented by calling
> > + * drm_mm_first_hole() and drm_mm_next_hole() which identify the
> > + * appropriate holes within the given range by efficiently traversing the
> > + * rbtree associated with @mm.
> > + */
> > +#define drm_mm_for_each_suitable_hole(pos, mm, range_start, range_end, \
> > +				      size, mode) \
> > +	for (pos = __drm_mm_first_hole(mm, range_start, range_end, size, \
> > +				       mode & ~DRM_MM_INSERT_ONCE); \
> > +	     pos; \
> > +	     pos = mode & DRM_MM_INSERT_ONCE ? \
> > +	     NULL : __drm_mm_next_hole(mm, pos, size, \
> > +				       mode & ~DRM_MM_INSERT_ONCE))
> > +
> >   /*
> >    * Basic range manager support (drm_mm.c)
> >    */