On Mon, 10 Feb 2025 13:43:17 +0000
Liviu Dudau <liviu.du...@arm.com> wrote:
> On Mon, Feb 10, 2025 at 02:18:07PM +0100, Boris Brezillon wrote:
> > On Mon, 10 Feb 2025 12:42:00 +0000
> > Adrián Larumbe <adrian.laru...@collabora.com> wrote:
> >
> > > A previous commit dealt with a similar situation, whereby upon enabling
> > > some mutex debug features, a warning about sleep muteces being used in a
> >
> > ^ mutexes
> >
> > > /proc file read atomic context was being triggered.
> > >
> > > Because in this case replacing the heap mutex with a spinlock isn't
> > > feasible, the fdinfo handler no longer traverses the list of heaps for
> > > every single VM associated with an open DRM file. Instad, when a new heap
> > > chunk is allocated, its size is accumulated into a VM-wide tally, which
> > > also makes the atomic context code path somewhat faster.
> > >
> > > Signed-off-by: Adrián Larumbe <adrian.laru...@collabora.com>
> > > Fixes: 3e2c8c718567 ("drm/panthor: Expose size of driver internal BO's
> > > over fdinfo")
> > > ---
> > > drivers/gpu/drm/panthor/panthor_heap.c | 38 ++++++++------------------
> > > drivers/gpu/drm/panthor/panthor_heap.h | 2 --
> > > drivers/gpu/drm/panthor/panthor_mmu.c | 18 +++++++-----
> > > drivers/gpu/drm/panthor/panthor_mmu.h | 1 +
> > > 4 files changed, 23 insertions(+), 36 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/panthor/panthor_heap.c
> > > b/drivers/gpu/drm/panthor/panthor_heap.c
> > > index db0285ce5812..686f209f5b09 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_heap.c
> > > +++ b/drivers/gpu/drm/panthor/panthor_heap.c
> > > @@ -127,6 +127,8 @@ static void panthor_free_heap_chunk(struct panthor_vm
> > > *vm,
> > > heap->chunk_count--;
> > > mutex_unlock(&heap->lock);
> > >
> > > + panthor_vm_heaps_accumulate(vm, -heap->chunk_size);
> > > +
> > > panthor_kernel_bo_destroy(chunk->bo);
> > > kfree(chunk);
> > > }
> > > @@ -180,6 +182,8 @@ static int panthor_alloc_heap_chunk(struct
> > > panthor_device *ptdev,
> > > heap->chunk_count++;
> > > mutex_unlock(&heap->lock);
> > >
> > > + panthor_vm_heaps_accumulate(vm, heap->chunk_size);
> > > +
> > > return 0;
> > >
> > > err_destroy_bo:
> > > @@ -389,6 +393,7 @@ int panthor_heap_return_chunk(struct
> > > panthor_heap_pool *pool,
> > > removed = chunk;
> > > list_del(&chunk->node);
> > > heap->chunk_count--;
> > > + panthor_vm_heaps_accumulate(chunk->bo->vm,
> > > -heap->chunk_size);
> > > break;
> > > }
> > > }
> > > @@ -560,6 +565,8 @@ panthor_heap_pool_create(struct panthor_device
> > > *ptdev, struct panthor_vm *vm)
> > > if (ret)
> > > goto err_destroy_pool;
> > >
> > > + panthor_vm_heaps_accumulate(vm, pool->gpu_contexts->obj->size);
> > > +
> > > return pool;
> > >
> > > err_destroy_pool:
> > > @@ -594,8 +601,11 @@ void panthor_heap_pool_destroy(struct
> > > panthor_heap_pool *pool)
> > > xa_for_each(&pool->xa, i, heap)
> > > drm_WARN_ON(&pool->ptdev->base,
> > > panthor_heap_destroy_locked(pool, i));
> > >
> > > - if (!IS_ERR_OR_NULL(pool->gpu_contexts))
> > > + if (!IS_ERR_OR_NULL(pool->gpu_contexts)) {
> > > + panthor_vm_heaps_accumulate(pool->gpu_contexts->vm,
> > > + -pool->gpu_contexts->obj->size);
> > > panthor_kernel_bo_destroy(pool->gpu_contexts);
> > > + }
> > >
> > > /* Reflects the fact the pool has been destroyed. */
> > > pool->vm = NULL;
> > > @@ -603,29 +613,3 @@ void panthor_heap_pool_destroy(struct
> > > panthor_heap_pool *pool)
> > >
> > > panthor_heap_pool_put(pool);
> > > }
> > > -
> > > -/**
> > > - * panthor_heap_pool_size() - Calculate size of all chunks across all
> > > heaps in a pool
> > > - * @pool: Pool whose total chunk size to calculate.
> > > - *
> > > - * This function adds the size of all heap chunks across all heaps in the
> > > - * argument pool. It also adds the size of the gpu contexts kernel bo.
> > > - * It is meant to be used by fdinfo for displaying the size of internal
> > > - * driver BO's that aren't exposed to userspace through a GEM handle.
> > > - *
> > > - */
> > > -size_t panthor_heap_pool_size(struct panthor_heap_pool *pool)
> > > -{
> > > - struct panthor_heap *heap;
> > > - unsigned long i;
> > > - size_t size = 0;
> > > -
> > > - down_read(&pool->lock);
> > > - xa_for_each(&pool->xa, i, heap)
> > > - size += heap->chunk_size * heap->chunk_count;
> > > - up_read(&pool->lock);
> > > -
> > > - size += pool->gpu_contexts->obj->size;
> > > -
> > > - return size;
> > > -}
> > > diff --git a/drivers/gpu/drm/panthor/panthor_heap.h
> > > b/drivers/gpu/drm/panthor/panthor_heap.h
> > > index e3358d4e8edb..25a5f2bba445 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_heap.h
> > > +++ b/drivers/gpu/drm/panthor/panthor_heap.h
> > > @@ -27,8 +27,6 @@ struct panthor_heap_pool *
> > > panthor_heap_pool_get(struct panthor_heap_pool *pool);
> > > void panthor_heap_pool_put(struct panthor_heap_pool *pool);
> > >
> > > -size_t panthor_heap_pool_size(struct panthor_heap_pool *pool);
> > > -
> > > int panthor_heap_grow(struct panthor_heap_pool *pool,
> > > u64 heap_gpu_va,
> > > u32 renderpasses_in_flight,
> > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c
> > > b/drivers/gpu/drm/panthor/panthor_mmu.c
> > > index 0a4e352b5505..aaad1a560805 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> > > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> > > @@ -345,6 +345,10 @@ struct panthor_vm {
> > >
> > > /** @heaps.lock: Lock used to protect access to @pool. */
> > > struct mutex lock;
> > > +
> > > + /** @heaps.size: Size of all chunks across all heaps in the
> > > pool. */
> > > + ssize_t size;
> >
> > Let's put that into an fdinfo struct.
> >
> > > +
> >
> > Drop the extra blank-line.
> >
> > > } heaps;
> > >
> > > /** @node: Used to insert the VM in the panthor_mmu::vm::list. */
> > > @@ -1539,6 +1543,7 @@ static void panthor_vm_destroy(struct panthor_vm
> > > *vm)
> > > mutex_lock(&vm->heaps.lock);
> > > panthor_heap_pool_destroy(vm->heaps.pool);
> > > vm->heaps.pool = NULL;
> > > + vm->heaps.size = 0;
> > > mutex_unlock(&vm->heaps.lock);
> > >
> > > drm_WARN_ON(&vm->ptdev->base,
> > > @@ -1963,13 +1968,7 @@ void panthor_vm_heaps_sizes(struct panthor_file
> > > *pfile, struct drm_memory_stats
> > >
> > > xa_lock(&pfile->vms->xa);
> > > xa_for_each(&pfile->vms->xa, i, vm) {
> > > - size_t size = 0;
> > > -
> > > - mutex_lock(&vm->heaps.lock);
> > > - if (vm->heaps.pool)
> > > - size = panthor_heap_pool_size(vm->heaps.pool);
> > > - mutex_unlock(&vm->heaps.lock);
> > > -
> > > + size_t size = vm->heaps.size;
> > > stats->resident += size;
> > > if (vm->as.id >= 0)
> > > stats->active += size;
> > > @@ -1977,6 +1976,11 @@ void panthor_vm_heaps_sizes(struct panthor_file
> > > *pfile, struct drm_memory_stats
> > > xa_unlock(&pfile->vms->xa);
> > > }
> > >
> > > +void panthor_vm_heaps_accumulate(struct panthor_vm *vm, ssize_t acc)
> > > +{
> >
> > Either there's some lock protecting this operation and we want a
> > lockdep_assert_held(), or we need to make it an atomic operation (and
> > make the size an atomic_t) to avoid races.
>
> If Adrián moves the call site in panthor_{alloc,free}_heap_chunk() before he
> drops the heap->lock,
> would that be sufficient? Pool create and destroy are hopefully race-free and
> panthor_heap_return_chunk() should be also safe.
I'm not sure that's enough. The tiler_oom_work is per-group, and you
can have multiple groups sharing the same VM. The workqueue we schedule
these works on is also not single-threaded, so you can potentially have
multiple threads updating the total VM tiler heap size at the same time.
