Re: [PATCH v2] drm/xe/ufence: Kick ufence immediately when possible

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Oct 17, 2024 at 11:42:37AM +0200, Nirmoy Das wrote:
> If the backing fence is signaled then signal ufence soon with
> system_wq. This should reduce load from the xe ordered_wq and also
> won't block signaling a ufence which doesn't require any serialization.
> 
> v2: fix system_wq typo
> 
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/1630
> Cc: Matthew Auld <matthew.auld@intel.com>
> gc: Matthew Brost <matthew.brost@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_sync.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c
> index c6cf227ead40..1a7907293088 100644
> --- a/drivers/gpu/drm/xe/xe_sync.c
> +++ b/drivers/gpu/drm/xe/xe_sync.c
> @@ -89,10 +89,14 @@ static void user_fence_worker(struct work_struct *w)
>  	user_fence_put(ufence);
>  }
>  
> -static void kick_ufence(struct xe_user_fence *ufence, struct dma_fence *fence)
> +static void kick_ufence(struct xe_user_fence *ufence, struct dma_fence *fence,
> +			bool signaled)

Predantic but maybe replace 'bool signaled' which a flag. We really want
to avoid bools if possible.

e.g.

#define UFENCE_FLAG_SIGNALED	BIT(0)

static void kick_ufence(struct xe_user_fence *ufence, struct dma_fence *fence,
			unsigned int flags)
{
	...
	if (flags & UFENCE_FLAG_SIGNALED)
		...
	else
		...
	...	
}

>  {
>  	INIT_WORK(&ufence->worker, user_fence_worker);
> -	queue_work(ufence->xe->ordered_wq, &ufence->worker);
> +	if (signaled)
> +		queue_work(system_wq, &ufence->worker);

I don't think you need the work queue here, just call the work func directly.

s/queue_work(system_wq, &ufence->worker)/user_fence_worker(&ufence->worker)

Matt

> +	else
> +		queue_work(ufence->xe->ordered_wq, &ufence->worker);
>  	dma_fence_put(fence);
>  }
>  
> @@ -100,7 +104,7 @@ static void user_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
>  {
>  	struct xe_user_fence *ufence = container_of(cb, struct xe_user_fence, cb);
>  
> -	kick_ufence(ufence, fence);
> +	kick_ufence(ufence, fence, false);
>  }
>  
>  int xe_sync_entry_parse(struct xe_device *xe, struct xe_file *xef,
> @@ -236,7 +240,7 @@ void xe_sync_entry_signal(struct xe_sync_entry *sync, struct dma_fence *fence)
>  		err = dma_fence_add_callback(fence, &sync->ufence->cb,
>  					     user_fence_cb);
>  		if (err == -ENOENT) {
> -			kick_ufence(sync->ufence, fence);
> +			kick_ufence(sync->ufence, fence, true);
>  		} else if (err) {
>  			XE_WARN_ON("failed to add user fence");
>  			user_fence_put(sync->ufence);
> -- 
> 2.46.0
>