[PATCH] drm/virtio: use kvmalloc for large allocations

[PATCH] drm/virtio: use kvmalloc for large allocations

[Sergey Senozhatsky]

We observed that some of virtio_gpu_object_shmem_init() allocations
can be rather costly - order 6 - which can be difficult to fulfill
under memory pressure conditions. Switch to kvmalloc_array() in
virtio_gpu_object_shmem_init() and let the kernel vmalloc the entries
array.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/gpu/drm/virtio/virtgpu_object.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index 2d3aa7baffe4..d9ad27e00905 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -184,8 +184,9 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev,
 		*nents = shmem->pages->orig_nents;
 	}
 
-	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
-			      GFP_KERNEL);
+	*ents = kvmalloc_array(*nents,
+			       sizeof(struct virtio_gpu_mem_entry),
+			       GFP_KERNEL);
 	if (!(*ents)) {
 		DRM_ERROR("failed to allocate ent list\n");
 		return -ENOMEM;
-- 
2.29.1.341.ge80a0c044ae-goog

Re: [PATCH] drm/virtio: use kvmalloc for large allocations

[Gerd Hoffmann]

  Hi,

> -	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
> -			      GFP_KERNEL);
> +	*ents = kvmalloc_array(*nents,
> +			       sizeof(struct virtio_gpu_mem_entry),
> +			       GFP_KERNEL);

Shouldn't that be balanced with a kvfree() elsewhere?

take care,
  Gerd

Re: [PATCH] drm/virtio: use kvmalloc for large allocations

[Sergey Senozhatsky]

Hi,

On (20/11/05 07:52), Gerd Hoffmann wrote:
> > -	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
> > -			      GFP_KERNEL);
> > +	*ents = kvmalloc_array(*nents,
> > +			       sizeof(struct virtio_gpu_mem_entry),
> > +			       GFP_KERNEL);
> 
> Shouldn't that be balanced with a kvfree() elsewhere?

I think it already is. ents pointer is assigned to vbuf->data_buf,
and free_vbuf() already uses kvfree(vbuf->data_buf) to free it.

	-ss

Re: [PATCH] drm/virtio: use kvmalloc for large allocations

[Gerd Hoffmann]

On Thu, Nov 05, 2020 at 04:00:54PM +0900, Sergey Senozhatsky wrote:
> Hi,
> 
> On (20/11/05 07:52), Gerd Hoffmann wrote:
> > > -	*ents = kmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),
> > > -			      GFP_KERNEL);
> > > +	*ents = kvmalloc_array(*nents,
> > > +			       sizeof(struct virtio_gpu_mem_entry),
> > > +			       GFP_KERNEL);
> > 
> > Shouldn't that be balanced with a kvfree() elsewhere?
> 
> I think it already is. ents pointer is assigned to vbuf->data_buf,
> and free_vbuf() already uses kvfree(vbuf->data_buf) to free it.

Ah, right, we needed that before elsewhere.
Ok then, pushed to drm-misc-next.

thanks,
  Gerd