From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 980C6C4338F for ; Thu, 29 Jul 2021 16:18:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8406C60EBB for ; Thu, 29 Jul 2021 16:18:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231350AbhG2QSl (ORCPT ); Thu, 29 Jul 2021 12:18:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60194 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231420AbhG2QSh (ORCPT ); Thu, 29 Jul 2021 12:18:37 -0400 Received: from mail-ot1-x335.google.com (mail-ot1-x335.google.com [IPv6:2607:f8b0:4864:20::335]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C020C0613C1 for ; Thu, 29 Jul 2021 09:18:33 -0700 (PDT) Received: by mail-ot1-x335.google.com with SMTP id c7-20020a9d27870000b02904d360fbc71bso6368651otb.10 for ; Thu, 29 Jul 2021 09:18:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=zmKveIAYbBTBnY55675WcFmTMajiGGjmMHwrRMhj8xk=; b=kA4MpBL0EpYu0CGamz/vCqUNLw+gHARamWO6i5IiCSuVfj53pppWlpjDuT5Rj5mZa6 a7j5jo2Y0i7apU/ms31YnrXZRjwnBTkYxn4u6pNyfB9BKC9cAlA2PEaNZyb8xdKCBs5U tO07e/lcsCP9fkfq6vJB/b3+Fqxz4X4Fnx+Pk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=zmKveIAYbBTBnY55675WcFmTMajiGGjmMHwrRMhj8xk=; b=alPzgNzpI3Fo/dJkwPyc4pGUrUHkS5IUUt4TLSEPJVKU+BGzoILI/qSycG6GZUjwXw QFhR83zQsF3DcA4rcBVgM0E1fdhODaFceYRXp/lwL0NS3do5QUT7sEu3VBrPobtLOqS2 oC0aHUvRL6UFhAUOlUDZJbsmkCeprD6itWGJJ1LCBI/JC0cby2sQKUYB2w1BkCSOoQvc 3+S/4yIUOCus7sCgLCl0Tfqyizgh4m0wM0XEhG2HI7FhyEsbhKrWSvYXlMko08KBUQ8/ BD4ZMp5hhRJCMU31aUt5384X6d0qZlDC4vBtUfe8DFGfQOUifC0p0Cvtlw+fbLlqJHgx uQ8A== X-Gm-Message-State: AOAM530zSq9oLt1X0IqAmuLbodqobYC0E8mBK+Sq1NN6X1iuYrpG48Sf Ia5MmiYtTQa8v+0MsMRGpMnhkJtqOeylzfgzUt4ADQ== X-Google-Smtp-Source: ABdhPJzBci/tj/bCUyHHuBvZPyafx8Ll/i7z8tWquHpWo8+lhjb+3Kyov65R2fGHOfU1n7A9ESrG+l7ZMH/VU3O7Yrs= X-Received: by 2002:a05:6830:2802:: with SMTP id w2mr3925202otu.303.1627575512650; Thu, 29 Jul 2021 09:18:32 -0700 (PDT) MIME-Version: 1.0 References: <20210726233854.2453899-1-robdclark@gmail.com> <20210726233854.2453899-2-robdclark@gmail.com> <50b181fe-6605-b7ac-36a6-8bcda2930e6f@gmail.com> <9edd7083-e6b3-b230-c273-8f2fbe76ca17@amd.com> <703dc9c3-5657-432e-ca0b-25bdd67a2abd@gmail.com> In-Reply-To: From: Daniel Vetter Date: Thu, 29 Jul 2021 18:18:21 +0200 Message-ID: Subject: Re: [RFC 1/4] dma-fence: Add deadline awareness To: Rob Clark Cc: =?UTF-8?Q?Christian_K=C3=B6nig?= , =?UTF-8?Q?Christian_K=C3=B6nig?= , dri-devel , Matthew Brost , Rob Clark , Sumit Semwal , Gustavo Padovan , "open list:SYNC FILE FRAMEWORK" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , open list Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 29, 2021 at 5:19 PM Rob Clark wrote: > > On Thu, Jul 29, 2021 at 12:03 AM Daniel Vetter wrote: > > > > On Wed, Jul 28, 2021 at 10:58:51AM -0700, Rob Clark wrote: > > > On Wed, Jul 28, 2021 at 10:23 AM Christian K=C3=B6nig > > > wrote: > > > > > > > > > > > > > > > > Am 28.07.21 um 17:15 schrieb Rob Clark: > > > > > On Wed, Jul 28, 2021 at 4:37 AM Christian K=C3=B6nig > > > > > wrote: > > > > >> Am 28.07.21 um 09:03 schrieb Christian K=C3=B6nig: > > > > >>> Am 27.07.21 um 16:25 schrieb Rob Clark: > > > > >>>> On Tue, Jul 27, 2021 at 12:11 AM Christian K=C3=B6nig > > > > >>>> wrote: > > > > >>>>> Am 27.07.21 um 01:38 schrieb Rob Clark: > > > > >>>>>> From: Rob Clark > > > > >>>>>> > > > > >>>>>> Add a way to hint to the fence signaler of an upcoming deadl= ine, > > > > >>>>>> such as > > > > >>>>>> vblank, which the fence waiter would prefer not to miss. Thi= s is to > > > > >>>>>> aid > > > > >>>>>> the fence signaler in making power management decisions, lik= e boosting > > > > >>>>>> frequency as the deadline approaches and awareness of missin= g > > > > >>>>>> deadlines > > > > >>>>>> so that can be factored in to the frequency scaling. > > > > >>>>>> > > > > >>>>>> Signed-off-by: Rob Clark > > > > >>>>>> --- > > > > >>>>>> 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/d= ma-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_f= ence > > > > >>>>>> **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 fe= nce 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 sign= aled > > > > >>>>>> by. This > > > > >>>>>> + * is intended to give feedback to the fence signaler to ai= d 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 =3D 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-f= ence.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 hrti= mer? > > > > >>>> > > > > >>>> We could push the ktime_t (and timer) down into the derived fe= nce > > > > >>>> class, but I think there is going to need to be some extra sto= rage > > > > >>>> *somewhere*.. maybe the fence signaler could get away with jus= t > > > > >>>> storing the nearest upcoming deadline per fence-context instea= d? > > > > >>> I would just push that into the driver instead. > > > > >>> > > > > >>> You most likely don't want the deadline per fence anyway in com= plex > > > > >>> scenarios, but rather per frame. And a frame is usually compose= d from > > > > >>> multiple fences. > > > > > Right, I ended up keeping track of the nearest deadline in patch = 5/4 > > > > > which added drm/msm support: > > > > > > > > > > https://nam11.safelinks.protection.outlook.com/?url=3Dhttps%3A= %2F%2Fpatchwork.freedesktop.org%2Fpatch%2F447138%2F&data=3D04%7C01%7Cch= ristian.koenig%40amd.com%7Cce6ace85263d448bbc9f08d951d9f06c%7C3dd8961fe4884= e608e11a82d994e183d%7C0%7C0%7C637630819606427306%7CUnknown%7CTWFpbGZsb3d8ey= JWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&= ;sdata=3DameszAOlClaZNeUDlYr37ZdIytVXNgiEUKuctjXLqZ0%3D&reserved=3D0 > > > > > > > > > > But if we do have the ktime_t in dma_fence in dma_fence, we can a= dd > > > > > some checks and avoid calling back to the driver if a later deadl= ine > > > > > is set on a fence that already has an earlier deadline. OTOH I > > > > > suppose I can push all that back to the driver to start, and we c= an > > > > > revisit once we have more drivers implementing deadline support. > > > > > > > > I still think that all of this is rather specific to your use case = and > > > > have strong doubt that anybody else will implement that. > > > > > > i915 does already have a similar thing in it's hand-rolled atomic > > > commit path. So I think msm won't be the only one. It should be als= o > > > useful to the other mobile GPUs with a gpu vs kms driver split, > > > although looking at the other gpu devfreq implementations, I don't > > > think they've yet gotten to this point in the fine tuning.. > > > > Yeah I have a dream that maybe i915 will use the atomic commit helpers,= I > > originally wrote them with i915 in mind :-) even had patches! > > > > I also think we'll need this eventually in other areas, Android also ha= s > > some hacks like this to make sure idle->first touch doesn't suck and > > similar things. > > input-boost is another thing I have on my roadmap.. part of the solution = is: > > commit 9bc95570175a7fbca29d86d22c54bbf399f4ad5a > Author: Rob Clark > AuthorDate: Mon Jul 26 07:46:50 2021 -0700 > Commit: Rob Clark > CommitDate: Tue Jul 27 17:54:36 2021 -0700 > > drm/msm: Devfreq tuning > > which gives the freq a bit of a nudge if the GPU has been idle for > longer than a certain threshold. > > But the other part is that if the GPU has been idle for more than 66ms > (typical autosuspend delay for adreno) it will suspend. For modern > adreno's it takes ~2ms to "boot up" the GPU from suspend. Which is > something you want to take out of the submit/execbuf path if you are > trying to reduce input-to-pageflip latency. > > We have a downstream patch that boosts the CPUs on input events (with > a cooldown period to prevent spacebar-heater) and I have been thinking > of something along those lines to trigger resuming the GPU.. it is > straightforward enough for touch based devices, but gets more > complicated with keyboard input. In particular, some keys you want to > trigger boost on key-release. Ie. modifier keys (ctrl/shift/alt/etc.. > the "search" key on chromebooks, etc) you want to boost on > key-release, not on key-press because unless you type *really* fast > you'll be in the cooldown period when the key-release event happens. > Unfortunately the kernel doesn't really know this "policy" sort of > information about which keys should boost on press vs release. So I > think the long-term/upstream solution is to do input-boost in > userspace.. sysfs already has all the knobs that a userspace > input-boost daemon would need to twiddle, so no real need for this to > be in the kernel. I guess the only drawback is the sysfs knobs are a > bit less standardized on the "desktop GPUs" which don't use devfreq. I think we could do a standard interface for this, either on the drm owner/master or somewhere in sysfs. Essentially "I expect to use the gpu for the very next frame, get it going". Across all hw there's a lot of things we can do. I think abuse is pretty easy to prevent with a cooldown or similar. -Daniel > > BR, > -R > > > -Daniel > > > > > > > > BR, > > > -R > > > > > > > >> Thinking more about it we could probably kill the spinlock point= er and > > > > >> make the flags 32bit if we absolutely need that here. > > > > > If we had a 'struct dma_fence_context' we could push the spinlock= , ops > > > > > pointer, and u64 context into that and replace with a single > > > > > dma_fence_context ptr, fwiw > > > > > > > > That won't work. We have a lot of use cases where you can't allocat= e > > > > memory, but must allocate a context. > > > > > > > > Christian. > > > > > > > > > > > > > > BR, > > > > > -R > > > > > > > > > >> But I still don't see the need for that, especially since most d= rivers > > > > >> probably won't implement it. > > > > >> > > > > >> Regards, > > > > >> Christian. > > > > >> > > > > >>> Regards, > > > > >>> Christian. > > > > >>> > > > > >>>> 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 mem= ber */ > > > > >>>>>> }; > > > > >>>>>> > > > > >>>>>> @@ -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 fenc= e > > > > >>>>>> signaler of an > > > > >>>>>> + * upcoming deadline, such as vblank, by which point t= he > > > > >>>>>> waiter would > > > > >>>>>> + * prefer the fence to be signaled by. This is intend= ed 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 struc= t > > > > >>>>>> 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); > > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch --=20 Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch