Re: [RFC v3 5/8] dmabuf: Add gpu cgroup charge transfer function

Hello.

On Wed, Mar 09, 2022 at 04:52:15PM +0000, "T.J. Mercier" tjmercier@google.com wrote:

+int dma_buf_charge_transfer(struct dma_buf *dmabuf, struct gpucg *gpucg) +{ +#ifdef CONFIG_CGROUP_GPU

• struct gpucg *current_gpucg;
• int ret = 0;
• /*

• * Verify that the cgroup of the process requesting the transfer is the
  

• * same as the one the buffer is currently charged to.
  

• */
  

• current_gpucg = gpucg_get(current);
• mutex_lock(&dmabuf->lock);
• if (current_gpucg != dmabuf->gpucg) {

• ret = -EPERM;
  

• goto err;
  

• }

Add a shortcut for gpucg == current_gpucg?

• ret = gpucg_try_charge(gpucg, dmabuf->gpucg_dev, dmabuf->size);
• if (ret)

• goto err;
  

• dmabuf->gpucg = gpucg;
• /* uncharge the buffer from the cgroup it's currently charged to. */
• gpucg_uncharge(current_gpucg, dmabuf->gpucg_dev, dmabuf->size);

I think gpucg_* API would need to cater for such transfers too since possibly transitional breach of a limit during the transfer may unnecessarily fail the operation.

My 0.02€, Michal