[PATCH 1/2] drm/mm: Add an iterator to optimally walk over holes for an allocation
Kasireddy, Vivek
vivek.kasireddy at intel.com
Thu Feb 3 09:08:58 UTC 2022
Hi Tvrtko,
> -----Original Message-----
> From: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Sent: Wednesday, February 02, 2022 5:04 AM
> To: Kasireddy, Vivek <vivek.kasireddy at intel.com>; dri-devel at lists.freedesktop.org
> Subject: Re: [PATCH 1/2] drm/mm: Add an iterator to optimally walk over holes for an
> allocation
>
>
> On 02/02/2022 01:13, 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 efficently 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.
> >
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > Signed-off-by: Vivek Kasireddy <vivek.kasireddy at intel.com>
> > ---
> > drivers/gpu/drm/drm_mm.c | 28 ++++++++++++----------------
> > include/drm/drm_mm.h | 32 ++++++++++++++++++++++++++++++++
> > 2 files changed, 44 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> > index 8257f9d4f619..416c849c10e5 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);
>
> May need to add kerneldoc since first/next_hole are now exported, or
> perhaps double underscore them if DRM core allows that approach to kind
> of signify "it is exported by shouldn't really be used"? Question for
> dri-devel I guess.
[Kasireddy, Vivek] Ok, will wait until Daniel or others on dri-devel weigh in.
However, it looks like double underscore is the way to go given how the
exported symbol __drm_mm_interval_first() is used.
>
> >
> > /**
> > * drm_mm_reserve_node - insert an pre-initialized node
> > @@ -520,7 +522,6 @@ int drm_mm_insert_node_in_range(struct drm_mm * const mm,
> > {
> > struct drm_mm_node *hole;
> > u64 remainder_mask;
> > - bool once;
> >
> > DRM_MM_BUG_ON(range_start > range_end);
> >
> > @@ -533,13 +534,8 @@ 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_best_hole(hole, mm, range_start, range_end, size, mode) {
> > 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..5055447697fa 100644
> > --- a/include/drm/drm_mm.h
> > +++ b/include/drm/drm_mm.h
> > @@ -322,6 +322,17 @@ static inline u64 __drm_mm_hole_node_end(const struct
> drm_mm_node *hole_node)
> > return list_next_entry(hole_node, node_list)->start;
> > }
> >
> > +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_hole_node_end - computes the end of the hole following @node
> > * @hole_node: drm_mm_node which implicitly tracks the following hole
> > @@ -400,6 +411,27 @@ static inline u64 drm_mm_hole_node_end(const struct
> drm_mm_node *hole_node)
> > 1 : 0; \
> > pos = list_next_entry(pos, hole_stack))
> >
> > +/**
> > + * drm_mm_for_each_best_hole - iterator to optimally walk over all holes >= @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 efficently traversing the
> > + * rbtree associated with @mm.
> > + */
> > +#define drm_mm_for_each_best_hole(pos, mm, range_start, range_end, size, mode) \
>
> Probably should not have "best" in the name since the mode is passed in
> by the caller.
[Kasireddy, Vivek] How about drm_mm_for_each_suitable_hole(...)?
>
> > + for (pos = drm_mm_first_hole(mm, range_start, range_end, size, mode); \
> > + pos; \
> > + pos = mode & DRM_MM_INSERT_ONCE ? \
> > + NULL : drm_mm_next_hole(mm, hole, size, mode))
>
> I think you would need to modify the first/next_hole to mask out
> DRM_MM_INSERT_ONCE, otherwise it probably does not work as it stands.
[Kasireddy, Vivek] Either that or I do the mask out in the macro itself:
#define drm_mm_for_each_best_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, hole, size, \
mode & ~DRM_MM_INSERT_ONCE))
and also take care of the locations where mode is checked in the loop.
Or, I could just retain the once bool and pass it to the macro. Not sure if this is ok
but there don't seem to be cleaner/elegant options.
Thanks,
Vivek
>
> Regards,
>
> Tvrtko
>
> > +
> > /*
> > * Basic range manager support (drm_mm.c)
> > */
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