[Intel-gfx] [PATCH 1/3] drm/i915: Keep track of request counts

[Daniel Vetter]

On Fri, Oct 28, 2011 at 10:55:27PM -0700, Ben Widawsky wrote:
> There is already a list of requests outstanding for a given client.
> Keeping a count is easy, and will give some information necessary to
> enable a more fair throttling scheme.
> 
> For now a client is uniquely identified by its file descriptor, however
> this may change in the future with new process APIs.
> 
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_drv.h |    1 +
>  drivers/gpu/drm/i915/i915_gem.c |    8 ++++++++
>  2 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 06a37f4..a251d22 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -919,6 +919,7 @@ struct drm_i915_file_private {
>  	struct {
>  		struct spinlock lock;
>  		struct list_head request_list;
> +		atomic_t outstanding_requests;

Here's your bikeshed:

Is the spinlock not sufficient to protect the count? I'm asking because
atomic_ts are pretty hard to extend to more fancy scheme (e.g. taking
actual gpu time into account or comparing this with other processes
outstanding_request to make better decisions).
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48