Re: [PATCH 2/2] drm/i915: add back the avail tracking

[Matthew Auld <matthew.auld@xxxxxxxxx>]

On 18/06/2021 14:44, Thomas Hellström wrote:
> On 6/18/21 3:31 PM, Matthew Auld wrote:
> > Looks like it got lost along the way, so add it back. This is needed for
> > the region query uAPI where we need to report an accurate available size
> > for lmem.
>
> Hmm. How is this uAPI intended to work in a multi-client environment 
> where the returned value can be nothing but a snapshot of the current 
> state, that can't be relied upon?

Ok, maybe I'm overselling it. s/accurate/current snapshot/. It does feel 
more useful than just returning -1 or so?

Daniel, Jason, any thoughts? Or maybe mr->total is all that real 
userspace really cares about?

> > This time around let's push it directly into the allocator, which
> > simplifies things, like not having to care about internal fragmentation,
> > or having to remember to track things for all possible interfaces that
> > might want to allocate or reserve pages.
> >
> > Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/i915_buddy.c             |  6 ++++++
> >   drivers/gpu/drm/i915/i915_buddy.h             |  1 +
> >   drivers/gpu/drm/i915/i915_debugfs.c           |  5 +++--
> >   drivers/gpu/drm/i915/i915_query.c             |  2 +-
> >   drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 13 +++++++++++++
> >   drivers/gpu/drm/i915/i915_ttm_buddy_manager.h |  2 ++
> >   drivers/gpu/drm/i915/intel_memory_region.c    |  8 ++++++++
> >   drivers/gpu/drm/i915/intel_memory_region.h    |  4 ++++
> >   8 files changed, 38 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_buddy.c 
> > b/drivers/gpu/drm/i915/i915_buddy.c
> > index 29dd7d0310c1..27cd2487a18f 100644
> > --- a/drivers/gpu/drm/i915/i915_buddy.c
> > +++ b/drivers/gpu/drm/i915/i915_buddy.c
> > @@ -80,6 +80,7 @@ int i915_buddy_init(struct i915_buddy_mm *mm, u64 
> > size, u64 chunk_size)
> >       size = round_down(size, chunk_size);
> >       mm->size = size;
> > +    mm->avail = size;
> >       mm->chunk_size = chunk_size;
> >       mm->max_order = ilog2(size) - ilog2(chunk_size);
> > @@ -159,6 +160,8 @@ void i915_buddy_fini(struct i915_buddy_mm *mm)
> >           i915_block_free(mm, mm->roots[i]);
> >       }
> > +    GEM_WARN_ON(mm->avail != mm->size);
> > +
> >       kfree(mm->roots);
> >       kfree(mm->free_list);
> >       kmem_cache_destroy(mm->slab_blocks);
> > @@ -235,6 +238,7 @@ void i915_buddy_free(struct i915_buddy_mm *mm,
> >                struct i915_buddy_block *block)
> >   {
> >       GEM_BUG_ON(!i915_buddy_block_is_allocated(block));
> > +    mm->avail += i915_buddy_block_size(mm, block);
> >       __i915_buddy_free(mm, block);
> >   }
> > @@ -288,6 +292,7 @@ i915_buddy_alloc(struct i915_buddy_mm *mm, 
> > unsigned int order)
> >       }
> >       mark_allocated(block);
> > +    mm->avail -= i915_buddy_block_size(mm, block);
> >       kmemleak_update_trace(block);
> >       return block;
> > @@ -373,6 +378,7 @@ int i915_buddy_alloc_range(struct i915_buddy_mm *mm,
> >               }
> >               mark_allocated(block);
> > +            mm->avail -= i915_buddy_block_size(mm, block);
> >               list_add_tail(&block->link, &allocated);
> >               continue;
> >           }
> > diff --git a/drivers/gpu/drm/i915/i915_buddy.h 
> > b/drivers/gpu/drm/i915/i915_buddy.h
> > index 37f8c42071d1..feb7c1bb6244 100644
> > --- a/drivers/gpu/drm/i915/i915_buddy.h
> > +++ b/drivers/gpu/drm/i915/i915_buddy.h
> > @@ -70,6 +70,7 @@ struct i915_buddy_mm {
> >       /* Must be at least PAGE_SIZE */
> >       u64 chunk_size;
> >       u64 size;
> > +    u64 avail;
> >   };
> >   static inline u64
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
> > b/drivers/gpu/drm/i915/i915_debugfs.c
> > index cc745751ac53..4765f220469e 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -246,8 +246,9 @@ static int i915_gem_object_info(struct seq_file 
> > *m, void *data)
> >              atomic_read(&i915->mm.free_count),
> >              i915->mm.shrink_memory);
> >       for_each_memory_region(mr, i915, id)
> > -        seq_printf(m, "%s: total:%pa, available:%pa bytes\n",
> > -               mr->name, &mr->total, &mr->avail);
> > +        seq_printf(m, "%s: total:%pa, available:%llu bytes\n",
> > +               mr->name, &mr->total,
> > +               intel_memory_region_get_avail(mr));
> >       return 0;
> >   }
> > diff --git a/drivers/gpu/drm/i915/i915_query.c 
> > b/drivers/gpu/drm/i915/i915_query.c
> > index e49da36c62fb..f10dcea94ac9 100644
> > --- a/drivers/gpu/drm/i915/i915_query.c
> > +++ b/drivers/gpu/drm/i915/i915_query.c
> > @@ -465,7 +465,7 @@ static int query_memregion_info(struct 
> > drm_i915_private *i915,
> >           info.region.memory_class = mr->type;
> >           info.region.memory_instance = mr->instance;
> >           info.probed_size = mr->total;
> > -        info.unallocated_size = mr->avail;
> > +        info.unallocated_size = intel_memory_region_get_avail(mr);
> >           if (__copy_to_user(info_ptr, &info, sizeof(info)))
> >               return -EFAULT;
> > diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c 
> > b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> > index fc7ad5c035b8..562d11edc5e4 100644
> > --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> > +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> > @@ -246,3 +246,16 @@ int i915_ttm_buddy_man_reserve(struct 
> > ttm_resource_manager *man,
> >       return ret;
> >   }
> > +/**
> > + * i915_ttm_buddy_man_avail - Get the currently available size
> > + * @man: The buddy allocator ttm manager
> > + *
> > + * Return: The available size in bytes
> > + */
> > +u64 i915_ttm_buddy_man_get_avail(struct ttm_resource_manager *man)
> > +{
> > +    struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
> > +    struct i915_buddy_mm *mm = &bman->mm;
> > +
> > +    return mm->avail;
> > +}
> > diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h 
> > b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> > index 26026213e20a..39f5b1a4c3e7 100644
> > --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> > +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> > @@ -53,4 +53,6 @@ int i915_ttm_buddy_man_fini(struct ttm_device *bdev,
> >   int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
> >                      u64 start, u64 size);
> > +u64 i915_ttm_buddy_man_get_avail(struct ttm_resource_manager *man);
> > +
> >   #endif
> > diff --git a/drivers/gpu/drm/i915/intel_memory_region.c 
> > b/drivers/gpu/drm/i915/intel_memory_region.c
> > index df59f884d37c..269cbb60e233 100644
> > --- a/drivers/gpu/drm/i915/intel_memory_region.c
> > +++ b/drivers/gpu/drm/i915/intel_memory_region.c
> > @@ -132,6 +132,14 @@ void intel_memory_region_set_name(struct 
> > intel_memory_region *mem,
> >       va_end(ap);
> >   }
> > +u64 intel_memory_region_get_avail(struct intel_memory_region *mr)
> > +{
> > +    if (mr->type == INTEL_MEMORY_LOCAL)
> > +        return i915_ttm_buddy_man_get_avail(mr->region_private);
> > +
> > +    return mr->avail;
> > +}
>
> Perhaps a kerneldoc comment here as well?
>
>
> > +
> >   static void __intel_memory_region_destroy(struct kref *kref)
> >   {
> >       struct intel_memory_region *mem =
> > diff --git a/drivers/gpu/drm/i915/intel_memory_region.h 
> > b/drivers/gpu/drm/i915/intel_memory_region.h
> > index 2be8433d373a..6f7a073d5a70 100644
> > --- a/drivers/gpu/drm/i915/intel_memory_region.h
> > +++ b/drivers/gpu/drm/i915/intel_memory_region.h
> > @@ -74,6 +74,7 @@ struct intel_memory_region {
> >       resource_size_t io_start;
> >       resource_size_t min_page_size;
> >       resource_size_t total;
> > +    /* Do not access directly. Use the accessor instead. */
> >       resource_size_t avail;
> >       u16 type;
> > @@ -125,4 +126,7 @@ intel_memory_region_set_name(struct 
> > intel_memory_region *mem,
> >   int intel_memory_region_reserve(struct intel_memory_region *mem,
> >                   resource_size_t offset,
> >                   resource_size_t size);
> > +
> > +u64 intel_memory_region_get_avail(struct intel_memory_region *mem);
> > +
> >   #endif
>
> Otherwise code itself looks good to me.
>
> Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>