Re: [dpdk-dev] [PATCH] gpudev: introduce memory API

[Thomas Monjalon <thomas@monjalon.net>]

03/06/2021 09:18, David Marchand:
> Quick pass:
> 
> On Wed, Jun 2, 2021 at 10:36 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > diff --git a/lib/gpudev/gpu_driver.h b/lib/gpudev/gpu_driver.h
> > new file mode 100644
> > index 0000000000..5ff609e49d
> > --- /dev/null
> > +++ b/lib/gpudev/gpu_driver.h
[...]
> > +struct rte_gpu_dev;
> > +
> > +typedef int (*gpu_malloc_t)(struct rte_gpu_dev *dev, size_t size, void **ptr);
> > +typedef int (*gpu_free_t)(struct rte_gpu_dev *dev, void *ptr);
> > +
> 
> Great to see this structure hidden in a driver-only header.
> 
> 
> > +struct rte_gpu_dev {
> 
> We could have a name[] field here, that will be later pointed at, in
> rte_gpu_info.
> Who is responsible for deciding of the device name?

The driver is responsible for the name of the device.
Yes I agree to store the name here.

> > +       /* Backing device. */
> > +       struct rte_device *device;
> > +       /* GPU info structure. */
> > +       struct rte_gpu_info info;
> > +       /* Counter of processes using the device. */
> > +       uint16_t process_cnt;
> > +       /* If device is currently used or not. */
> > +       enum rte_gpu_state state;
> > +       /* FUNCTION: Allocate memory on the GPU. */
> > +       gpu_malloc_t gpu_malloc;
> > +       /* FUNCTION: Allocate memory on the CPU visible from the GPU. */
> > +       gpu_malloc_t gpu_malloc_visible;
> > +       /* FUNCTION: Free allocated memory on the GPU. */
> > +       gpu_free_t gpu_free;
> > +       /* Device interrupt handle. */
> > +       struct rte_intr_handle *intr_handle;
> > +       /* Driver-specific private data. */
> > +       void *dev_private;
> > +} __rte_cache_aligned;
> > +
> > +struct rte_gpu_dev *rte_gpu_dev_allocate(const char *name);
> > +struct rte_gpu_dev *rte_gpu_dev_get_by_name(const char *name);
> 
> Those symbols will have to be marked internal (__rte_internal +
> version.map) for drivers to see them.

OK, good catch.

[...]
> > +/** Maximum number of GPU engines. */
> > +#define RTE_GPU_MAX_DEVS UINT16_C(32)
> 
> Bleh.
> Let's stop with max values.
> The iterator _next should return a special value indicating there is
> no more devs to list.

I fully agree.
I would like to define gpu_id as an int to simplify comparisons
with error value. int or int16_t ?

> > +/** Maximum length of device name. */
> > +#define RTE_GPU_NAME_MAX_LEN 128

Will be dropped as well.

> > +
> > +/** Flags indicate current state of GPU device. */
> > +enum rte_gpu_state {
> > +       RTE_GPU_STATE_UNUSED,        /**< not initialized */
> > +       RTE_GPU_STATE_INITIALIZED,   /**< initialized */
> > +};
> > +
> > +/** Store a list of info for a given GPU. */
> > +struct rte_gpu_info {
> > +       /** GPU device ID. */
> > +       uint16_t gpu_id;
> > +       /** Unique identifier name. */
> > +       char name[RTE_GPU_NAME_MAX_LEN];
> 
> const char *name;
> 
> Then the gpu generic layer simply fills this with the
> rte_gpu_dev->name field I proposed above.

Yes.

> > +       /** Total memory available on device. */
> > +       size_t total_memory;
> > +       /** Total processors available on device. */
> > +       int processor_count;
> > +};