Re: [RFC v4 4/8] dmabuf: heaps: export system_heap buffers with GPU cgroup charging

["T.J. Mercier" <tjmercier@google.com>]

On Tue, Mar 29, 2022 at 1:42 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Mon, Mar 28, 2022 at 11:28:24AM -0700, T.J. Mercier wrote:
> > On Mon, Mar 28, 2022 at 7:36 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > >
> > > On Mon, Mar 28, 2022 at 03:59:43AM +0000, T.J. Mercier wrote:
> > > > From: Hridya Valsaraju <hridya@google.com>
> > > >
> > > > All DMA heaps now register a new GPU cgroup device upon creation, and the
> > > > system_heap now exports buffers associated with its GPU cgroup device for
> > > > tracking purposes.
> > > >
> > > > Signed-off-by: Hridya Valsaraju <hridya@google.com>
> > > > Signed-off-by: T.J. Mercier <tjmercier@google.com>
> > > >
> > > > ---
> > > > v3 changes
> > > > Use more common dual author commit message format per John Stultz.
> > > >
> > > > v2 changes
> > > > Move dma-buf cgroup charge transfer from a dma_buf_op defined by every
> > > > heap to a single dma-buf function for all heaps per Daniel Vetter and
> > > > Christian König.
> > >
> > > Apologies for being out of the loop quite a bit. I scrolled through this
> > > all and I think it looks good to get going.
> > >
> > > The only thing I have is whether we should move the cgroup controllers out
> > > of dma-buf heaps, since that's rather android centric. E.g.
> > > - a system gpucg_device which is used by all the various single page
> > >   allocators (dma-buf heap but also shmem helpers and really anything
> > >   else)
> > > - same for cma, again both for dma-buf heaps and also for the gem cma
> > >   helpers in drm
> >
> > Thanks Daniel, in general that makes sense to me as an approach to
> > making this more universal. However for the Android case I'm not sure
> > if the part about a single system gpucg_device would be sufficient,
> > because there are at least 12 different graphics related heaps that
> > could potentially be accounted/limited differently. [1]  So that
> > raises the question of how fine grained we want this to be... I tend
> > towards separating them all, but I haven't formed a strong opinion
> > about this at the moment. It sounds like you are in favor of a
> > smaller, more rigidly defined set of them? Either way, we need to add
> > code for accounting at points where we know memory is specifically for
> > graphics use and not something else right? (I.E. Whether it is a
> > dma-buf heap or somewhere like drm_gem_object_init.) So IIUC the only
> > question is what to use for the gpucg_device(s) at these locations.
>
> We don't have 12 in upstream, so this is a lot easier here :-)
>
> I'm not exactly sure why you have such a huge pile of them.
>
> For gem buffers it would be fairly similar to what you've done for dma-buf
> heaps I think, with the various helper libraries (drivers stopped
> hand-rolling their gem buffer) setting the right accounting group. And
> yeah for system memory I think we'd need to have standard ones, for driver
> specific ones it's kinda different.
>
> > [1] https://cs.android.com/android/platform/superproject/+/master:hardware/google/graphics/common/libion/ion.cpp;l=39-50
> >
> > >
> > > Otherwise this will only work on non-upstream android where gpu drivers
> > > allocate everything from dma-buf heap. If you use something like the x86
> > > android project with mesa drivers, then driver-internal buffers will be
> > > allocated through gem and not through dma-buf heaps. Or at least I think
> > > that's how it works.
> > >
> > > But also meh, we can fix this fairly easily later on by adding these
> > > standard gpucg_dev somwehere with a bit of kerneldoc.
> >
> > This is what I was thinking would happen next, but IDK if anyone sees
> > a more central place to do this type of use-specific accounting.
>
> Hm I just realized ... are the names in the groups abi? If yes then I
> think we need to fix this before we merge anything.
> -Daniel

Do you mean the set of possible names being part of the ABI for GPU
cgroups? I'm not exactly sure what you mean here.

The name is a settable string inside the gpucg_device struct, and
right now the docs say it must be from a string literal but this can
be changed. The only one this patchset adds is "system", which comes
from the name field in its dma_heap_export_info struct when it's first
created (and that string is hardcoded). The heap gpucg_devices are all
registered from one spot in dma-heap.c, so maybe we should append
"-heap" to the gpucg_device names there so "system" is available for a
standardized name. Let me make those two changes, and I will also
rebase this series before resending.



>
> >
> > >
> > > Anyway has my all my ack, but don't count this as my in-depth review :-)
> > > -Daniel
> >
> > Thanks again for taking a look!
> > >
> > > > ---
> > > >  drivers/dma-buf/dma-heap.c          | 27 +++++++++++++++++++++++++++
> > > >  drivers/dma-buf/heaps/system_heap.c |  3 +++
> > > >  include/linux/dma-heap.h            | 11 +++++++++++
> > > >  3 files changed, 41 insertions(+)
> > > >
> > > > diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> > > > index 8f5848aa144f..885072427775 100644
> > > > --- a/drivers/dma-buf/dma-heap.c
> > > > +++ b/drivers/dma-buf/dma-heap.c
> > > > @@ -7,6 +7,7 @@
> > > >   */
> > > >
> > > >  #include <linux/cdev.h>
> > > > +#include <linux/cgroup_gpu.h>
> > > >  #include <linux/debugfs.h>
> > > >  #include <linux/device.h>
> > > >  #include <linux/dma-buf.h>
> > > > @@ -31,6 +32,7 @@
> > > >   * @heap_devt                heap device node
> > > >   * @list             list head connecting to list of heaps
> > > >   * @heap_cdev                heap char device
> > > > + * @gpucg_dev                gpu cgroup device for memory accounting
> > > >   *
> > > >   * Represents a heap of memory from which buffers can be made.
> > > >   */
> > > > @@ -41,6 +43,9 @@ struct dma_heap {
> > > >       dev_t heap_devt;
> > > >       struct list_head list;
> > > >       struct cdev heap_cdev;
> > > > +#ifdef CONFIG_CGROUP_GPU
> > > > +     struct gpucg_device gpucg_dev;
> > > > +#endif
> > > >  };
> > > >
> > > >  static LIST_HEAD(heap_list);
> > > > @@ -216,6 +221,26 @@ const char *dma_heap_get_name(struct dma_heap *heap)
> > > >       return heap->name;
> > > >  }
> > > >
> > > > +#ifdef CONFIG_CGROUP_GPU
> > > > +/**
> > > > + * dma_heap_get_gpucg_dev() - get struct gpucg_device for the heap.
> > > > + * @heap: DMA-Heap to get the gpucg_device struct for.
> > > > + *
> > > > + * Returns:
> > > > + * The gpucg_device struct for the heap. NULL if the GPU cgroup controller is
> > > > + * not enabled.
> > > > + */
> > > > +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap)
> > > > +{
> > > > +     return &heap->gpucg_dev;
> > > > +}
> > > > +#else /* CONFIG_CGROUP_GPU */
> > > > +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap)
> > > > +{
> > > > +     return NULL;
> > > > +}
> > > > +#endif /* CONFIG_CGROUP_GPU */
> > > > +
> > > >  struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
> > > >  {
> > > >       struct dma_heap *heap, *h, *err_ret;
> > > > @@ -288,6 +313,8 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
> > > >       list_add(&heap->list, &heap_list);
> > > >       mutex_unlock(&heap_list_lock);
> > > >
> > > > +     gpucg_register_device(dma_heap_get_gpucg_dev(heap), exp_info->name);
> > > > +
> > > >       return heap;
> > > >
> > > >  err2:
> > > > diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> > > > index ab7fd896d2c4..752a05c3cfe2 100644
> > > > --- a/drivers/dma-buf/heaps/system_heap.c
> > > > +++ b/drivers/dma-buf/heaps/system_heap.c
> > > > @@ -395,6 +395,9 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
> > > >       exp_info.ops = &system_heap_buf_ops;
> > > >       exp_info.size = buffer->len;
> > > >       exp_info.flags = fd_flags;
> > > > +#ifdef CONFIG_CGROUP_GPU
> > > > +     exp_info.gpucg_dev = dma_heap_get_gpucg_dev(heap);
> > > > +#endif
> > > >       exp_info.priv = buffer;
> > > >       dmabuf = dma_buf_export(&exp_info);
> > > >       if (IS_ERR(dmabuf)) {
> > > > diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
> > > > index 0c05561cad6e..e447a61d054e 100644
> > > > --- a/include/linux/dma-heap.h
> > > > +++ b/include/linux/dma-heap.h
> > > > @@ -10,6 +10,7 @@
> > > >  #define _DMA_HEAPS_H
> > > >
> > > >  #include <linux/cdev.h>
> > > > +#include <linux/cgroup_gpu.h>
> > > >  #include <linux/types.h>
> > > >
> > > >  struct dma_heap;
> > > > @@ -59,6 +60,16 @@ void *dma_heap_get_drvdata(struct dma_heap *heap);
> > > >   */
> > > >  const char *dma_heap_get_name(struct dma_heap *heap);
> > > >
> > > > +/**
> > > > + * dma_heap_get_gpucg_dev() - get a pointer to the struct gpucg_device for the
> > > > + * heap.
> > > > + * @heap: DMA-Heap to retrieve gpucg_device for.
> > > > + *
> > > > + * Returns:
> > > > + * The gpucg_device struct for the heap.
> > > > + */
> > > > +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap);
> > > > +
> > > >  /**
> > > >   * dma_heap_add - adds a heap to dmabuf heaps
> > > >   * @exp_info:                information needed to register this heap
> > > > --
> > > > 2.35.1.1021.g381101b075-goog
> > > >
> > >
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch