From: Rob Clark <robdclark@gmail.com>
To: "Christian König" <ckoenig.leichtzumerken@gmail.com>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Matthew Brost" <matthew.brost@intel.com>,
"Rob Clark" <robdclark@chromium.org>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Gustavo Padovan" <gustavo@padovan.org>,
"Christian König" <christian.koenig@amd.com>,
"open list:SYNC FILE FRAMEWORK" <linux-media@vger.kernel.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@lists.linaro.org>,
"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 1/4] dma-fence: Add deadline awareness
Date: Tue, 27 Jul 2021 07:25:24 -0700 [thread overview]
Message-ID: <CAF6AEGuNxi_aeYE37FT3a-atCUWgepxs-9EwxMfpiMaU7wgqdQ@mail.gmail.com> (raw)
In-Reply-To: <50b181fe-6605-b7ac-36a6-8bcda2930e6f@gmail.com>
On Tue, Jul 27, 2021 at 12:11 AM Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Am 27.07.21 um 01:38 schrieb Rob Clark:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > Add a way to hint to the fence signaler of an upcoming deadline, such as
> > vblank, which the fence waiter would prefer not to miss. This is to aid
> > the fence signaler in making power management decisions, like boosting
> > frequency as the deadline approaches and awareness of missing deadlines
> > so that can be factored in to the frequency scaling.
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > ---
> > drivers/dma-buf/dma-fence.c | 39 +++++++++++++++++++++++++++++++++++++
> > include/linux/dma-fence.h | 17 ++++++++++++++++
> > 2 files changed, 56 insertions(+)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index ce0f5eff575d..2e0d25ab457e 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -910,6 +910,45 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
> > }
> > EXPORT_SYMBOL(dma_fence_wait_any_timeout);
> >
> > +
> > +/**
> > + * dma_fence_set_deadline - set desired fence-wait deadline
> > + * @fence: the fence that is to be waited on
> > + * @deadline: the time by which the waiter hopes for the fence to be
> > + * signaled
> > + *
> > + * Inform the fence signaler of an upcoming deadline, such as vblank, by
> > + * which point the waiter would prefer the fence to be signaled by. This
> > + * is intended to give feedback to the fence signaler to aid in power
> > + * management decisions, such as boosting GPU frequency if a periodic
> > + * vblank deadline is approaching.
> > + */
> > +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> > +{
> > + unsigned long flags;
> > +
> > + if (dma_fence_is_signaled(fence))
> > + return;
> > +
> > + spin_lock_irqsave(fence->lock, flags);
> > +
> > + /* If we already have an earlier deadline, keep it: */
> > + if (test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &fence->flags) &&
> > + ktime_before(fence->deadline, deadline)) {
> > + spin_unlock_irqrestore(fence->lock, flags);
> > + return;
> > + }
> > +
> > + fence->deadline = deadline;
> > + set_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &fence->flags);
> > +
> > + spin_unlock_irqrestore(fence->lock, flags);
> > +
> > + if (fence->ops->set_deadline)
> > + fence->ops->set_deadline(fence, deadline);
> > +}
> > +EXPORT_SYMBOL(dma_fence_set_deadline);
> > +
> > /**
> > * dma_fence_init - Initialize a custom fence.
> > * @fence: the fence to initialize
> > diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> > index 6ffb4b2c6371..4e6cfe4e6fbc 100644
> > --- a/include/linux/dma-fence.h
> > +++ b/include/linux/dma-fence.h
> > @@ -88,6 +88,7 @@ struct dma_fence {
> > /* @timestamp replaced by @rcu on dma_fence_release() */
> > struct rcu_head rcu;
> > };
> > + ktime_t deadline;
>
> Mhm, adding the flag sounds ok to me but I'm a bit hesitating adding the
> deadline as extra field here.
>
> We tuned the dma_fence structure intentionally so that it is only 64 bytes.
Hmm, then I guess you wouldn't be a fan of also adding an hrtimer?
We could push the ktime_t (and timer) down into the derived fence
class, but I think there is going to need to be some extra storage
*somewhere*.. maybe the fence signaler could get away with just
storing the nearest upcoming deadline per fence-context instead?
BR,
-R
> Regards,
> Christian.
>
> > u64 context;
> > u64 seqno;
> > unsigned long flags;
> > @@ -99,6 +100,7 @@ enum dma_fence_flag_bits {
> > DMA_FENCE_FLAG_SIGNALED_BIT,
> > DMA_FENCE_FLAG_TIMESTAMP_BIT,
> > DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
> > + DMA_FENCE_FLAG_HAS_DEADLINE_BIT,
> > DMA_FENCE_FLAG_USER_BITS, /* must always be last member */
> > };
> >
> > @@ -261,6 +263,19 @@ struct dma_fence_ops {
> > */
> > void (*timeline_value_str)(struct dma_fence *fence,
> > char *str, int size);
> > +
> > + /**
> > + * @set_deadline:
> > + *
> > + * Callback to allow a fence waiter to inform the fence signaler of an
> > + * upcoming deadline, such as vblank, by which point the waiter would
> > + * prefer the fence to be signaled by. This is intended to give feedback
> > + * to the fence signaler to aid in power management decisions, such as
> > + * boosting GPU frequency.
> > + *
> > + * This callback is optional.
> > + */
> > + void (*set_deadline)(struct dma_fence *fence, ktime_t deadline);
> > };
> >
> > void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
> > @@ -586,6 +601,8 @@ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
> > return ret < 0 ? ret : 0;
> > }
> >
> > +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline);
> > +
> > struct dma_fence *dma_fence_get_stub(void);
> > struct dma_fence *dma_fence_allocate_private_stub(void);
> > u64 dma_fence_context_alloc(unsigned num);
>
next prev parent reply other threads:[~2021-07-27 14:21 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 23:38 [RFC 0/4] dma-fence: Deadline awareness Rob Clark
2021-07-26 23:38 ` [RFC 1/4] dma-fence: Add deadline awareness Rob Clark
2021-07-27 7:11 ` Christian König
2021-07-27 14:25 ` Rob Clark [this message]
2021-07-28 7:03 ` Christian König
2021-07-28 11:37 ` Christian König
2021-07-28 15:15 ` Rob Clark
2021-07-28 17:23 ` Christian König
2021-07-28 17:58 ` Rob Clark
2021-07-29 7:03 ` Daniel Vetter
2021-07-29 15:23 ` Rob Clark
2021-07-29 16:18 ` Daniel Vetter
2021-07-29 17:32 ` Rob Clark
2021-07-26 23:38 ` [RFC 2/4] drm/vblank: Add helper to get next vblank time Rob Clark
2021-07-26 23:38 ` [RFC 3/4] drm/atomic-helper: Set fence deadline for vblank Rob Clark
2021-07-27 10:44 ` Michel Dänzer
2021-07-27 14:33 ` Rob Clark
2021-07-26 23:38 ` [RFC 4/4] drm/scheduler: Add fence deadline support Rob Clark
2021-07-26 23:51 ` [RFC 0/4] dma-fence: Deadline awareness Rob Clark
2021-07-27 14:41 ` Michel Dänzer
2021-07-27 15:12 ` Rob Clark
2021-07-27 15:19 ` Michel Dänzer
2021-07-27 15:37 ` Rob Clark
2021-07-28 11:36 ` Christian König
2021-07-28 13:08 ` Michel Dänzer
2021-07-28 13:13 ` Christian König
2021-07-28 13:24 ` Michel Dänzer
2021-07-28 13:31 ` Christian König
2021-07-28 13:57 ` Pekka Paalanen
2021-07-28 14:30 ` Christian König
2021-07-29 8:08 ` Michel Dänzer
2021-07-29 8:23 ` Pekka Paalanen
2021-07-29 8:43 ` Christian König
2021-07-29 9:15 ` Pekka Paalanen
2021-07-29 10:14 ` Christian König
2021-07-29 10:28 ` Michel Dänzer
2021-07-29 11:00 ` Pekka Paalanen
2021-07-29 11:43 ` Christian König
2021-07-29 12:49 ` Pekka Paalanen
2021-07-29 13:41 ` Christian König
2021-07-29 14:10 ` Pekka Paalanen
2021-07-28 15:27 ` Rob Clark
2021-07-28 17:20 ` Christian König
2021-07-28 15:34 ` Rob Clark
2021-07-29 7:09 ` Daniel Vetter
2021-07-29 8:17 ` Michel Dänzer
2021-07-29 9:03 ` Daniel Vetter
2021-07-29 9:37 ` Pekka Paalanen
2021-07-29 12:18 ` Daniel Vetter
2021-07-29 12:59 ` Pekka Paalanen
2021-07-29 14:05 ` Daniel Vetter
2021-07-27 21:17 ` [RFC 5/4] drm/msm: Add deadline based boost support Rob Clark
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