[Mesa-dev] [EGL android: accquire fence implementation] i965: Queue the buffer with a sync fence for Android OS

Tue Jul 11 16:09:46 UTC 2017

Hello Figa, Few caveats on that approach

> -----Original Message-----
> From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org] On Behalf
> Of Tomasz Figa
> Sent: Tuesday, July 11, 2017 8:58 PM
> To: Wu, Zhongmin <zhongmin.wu at intel.com>
> Cc: Gao, Shuo <shuo.gao at intel.com>; Liu, Zhiquan <zhiquan.liu at intel.com>;
> ML mesa-dev <mesa-dev at lists.freedesktop.org>; Emil Velikov
> <emil.l.velikov at gmail.com>; Chad Versace <chadversary at chromium.org>; Eric
> Engestrom <eric at engestrom.ch>; Marathe, Yogesh
> <yogesh.marathe at intel.com>; Rob Clark <robclark at freedesktop.org>; Kenneth
> Graunke <kenneth at whitecape.org>; Widawsky, Benjamin
> <benjamin.widawsky at intel.com>; Kondapally, Kalyan
> <kalyan.kondapally at intel.com>; Kristian H . Kristensen
> <hoegsberg at chromium.org>; Timothy Arceri <tarceri at itsqueeze.com>
> Subject: Re: [Mesa-dev] [EGL android: accquire fence implementation] i965:
> Queue the buffer with a sync fence for Android OS
> 
> Now for real, sorry guys... (Seriously gmail why you do this to me.)
> 
> -chuanbo.weng at intel.com (bounces)
> +"Gao, Shuo" <shuo.gao at intel.com> (forgot to add originally, sorry)
> 
> On Wed, Jul 12, 2017 at 12:23 AM, Tomasz Figa <tfiga at chromium.org> wrote:
> > Hi Zhongmin,
> >
> > On Tue, Jul 11, 2017 at 11:02 AM, Wu, Zhongmin <zhongmin.wu at intel.com>
> wrote:
> >> By the way,
> >>
> >> For cancelBuffer, sorry I forget such function, thanks for notice. It should
> also pass the same fence fd as the queuebuffer.
> >>
> >> And Yogesh, you mentioned the gallium,   is it another platform supported by
> mesa ?  I am sorry I have no idea about this,  could you please help to check this
> ?
> >>
> >> I think we can co-work with mesa team to work out an acceptable fix which
> can meet the requirement of Android without any break on other platforms.
> >
> > One thing needs clarifying here. Release fences from EGL are _not_ a
> > requirement. It is an optional feature. Android compliance suites pass
> > fully without Android sync fence support in Mesa at all.
> >
> > Other than that, it's been taking long enough and I agree that we
> > should finally wire both acquire and release fence support in EGL and
> > related drivers. Otherwise we can forget about getting good user
> > experience on Android.
> >
> > On a technical side, the EGL change needs to take into account that
> > not all drivers support fences and so it needs to have a fallback to
> > old behavior for those which don't.
> >
> > Other than that, correct me if I'm wrong, but could we just use the
> > DRI2 fence extension instead of adding some custom callbacks? I can
> > see that a normal client request to create a sync fence would end up
> > calling dri2_dpy->fence->create_fence_fd() (if it's present) [1].
> > Could we do the same?

May be here we need to look at complete sequence
eglCreateSyncKHR ->  _eglCreateSync -> dri2_create_sync, 
as eglCreateSyncKHR  seems entry point and its doing attrib/type checks
before reaching  dri2_create_sync(). Also, dri2_create_sync is static, 
can't be called directly, there needs to be an entry point / interface.

> >
> > [1]
> > https://cgit.freedesktop.org/mesa/mesa/tree/src/egl/drivers/dri2/egl_d
> > ri2.c#n2772
> >
> > + Kristian, Chad and Dominik who have been looking into sync fence
> > integration with our EGL drivers.
> >
> > Best regards,
> > Tomasz
> >
> >>
> >> -----Original Message-----
> >> From: Wu, Zhongmin
> >> Sent: Tuesday, July 11, 2017 8:40
> >> To: 'Emil Velikov' <emil.l.velikov at gmail.com>; Marathe, Yogesh
> >> <yogesh.marathe at intel.com>
> >> Cc: Widawsky, Benjamin <benjamin.widawsky at intel.com>; Liu, Zhiquan
> >> <zhiquan.liu at intel.com>; Eric Engestrom <eric at engestrom.ch>; Rob
> >> Clark <robclark at freedesktop.org>; Tomasz Figa <tfiga at chromium.org>;
> >> Kenneth Graunke <kenneth at whitecape.org>; Kondapally, Kalyan
> >> <kalyan.kondapally at intel.com>; ML mesa-dev
> >> <mesa-dev at lists.freedesktop.org>; Timothy Arceri
> >> <tarceri at itsqueeze.com>; Chuanbo Weng <chuanbo.weng at intel.com>
> >> Subject: RE: [Mesa-dev] [EGL android: accquire fence implementation]
> >> i965: Queue the buffer with a sync fence for Android OS
> >>
> >> Hi Emil and Yogesh
> >> Thank you for your comments,  and thanks Yogesh for giving the
> >> detailed explanations
> >>
> >>
> >> And according to the document of Android below
> (https://source.android.com/devices/graphics/arch-bq-gralloc):
> >>
> >> Recent Android devices support the sync framework, which enables the
> system to do nifty things when combined with hardware components that can
> manipulate graphics data asynchronously. For example, a producer can submit a
> series of OpenGL ES drawing commands and then enqueue the output buffer
> before rendering completes. The buffer is accompanied by a fence that signals
> when the contents are ready.
> >>
> >>
> >> I think the things is very clear, that is if the rendering is completed already
> when we call queueBuffer() in mesa ?   If not, we should queue the buffer with a
> fence which will be signaled when the buffer is ready.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: Emil Velikov [mailto:emil.l.velikov at gmail.com]
> >> Sent: Tuesday, July 11, 2017 1:18
> >> To: Marathe, Yogesh <yogesh.marathe at intel.com>
> >> Cc: Wu, Zhongmin <zhongmin.wu at intel.com>; Widawsky, Benjamin
> >> <benjamin.widawsky at intel.com>; Liu, Zhiquan <zhiquan.liu at intel.com>;
> >> Eric Engestrom <eric at engestrom.ch>; Rob Clark
> >> <robclark at freedesktop.org>; Tomasz Figa <tfiga at chromium.org>; Kenneth
> >> Graunke <kenneth at whitecape.org>; Kondapally, Kalyan
> >> <kalyan.kondapally at intel.com>; ML mesa-dev
> >> <mesa-dev at lists.freedesktop.org>; Timothy Arceri
> >> <tarceri at itsqueeze.com>; Chuanbo Weng <chuanbo.weng at intel.com>
> >> Subject: Re: [Mesa-dev] [EGL android: accquire fence implementation]
> >> i965: Queue the buffer with a sync fence for Android OS
> >>
> >> On 10 July 2017 at 15:26, Marathe, Yogesh <yogesh.marathe at intel.com>
> wrote:
> >>> Hello Emil, My two cents since I too spent some time on this.
> >>>
> >>>> -----Original Message-----
> >>>> From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org] On
> >>>> Behalf Of Emil Velikov
> >>>> Sent: Monday, July 10, 2017 4:41 PM
> >>>> To: Wu, Zhongmin <zhongmin.wu at intel.com>
> >>>> Cc: Widawsky, Benjamin <benjamin.widawsky at intel.com>; Liu, Zhiquan
> >>>> <zhiquan.liu at intel.com>; Eric Engestrom <eric at engestrom.ch>; Rob
> >>>> Clark <robclark at freedesktop.org>; Tomasz Figa <tfiga at chromium.org>;
> >>>> Kenneth Graunke <kenneth at whitecape.org>; Kondapally, Kalyan
> >>>> <kalyan.kondapally at intel.com>; ML mesa-dev <mesa-
> >>>> dev at lists.freedesktop.org>; Timothy Arceri <tarceri at itsqueeze.com>;
> >>>> Chuanbo Weng <chuanbo.weng at intel.com>
> >>>> Subject: Re: [Mesa-dev] [EGL android: accquire fence implementation]
> i965:
> >>>> Queue the buffer with a sync fence for Android OS
> >>>>
> >>>> Hi Zhongmin Wu,
> >>>>
> >>>> Above all, a bit of a disclaimer: I'm by no means an expert on the
> >>>> topic so take the following with a pinch of salt.
> >>>>
> >>>> On 10 July 2017 at 03:11, Zhongmin Wu <zhongmin.wu at intel.com> wrote:
> >>>> > Before we queued the buffer with a invalid fence (-1), it will
> >>>> > make some benchmarks failed to test such as flatland.
> >>>> >
> >>>> > Now we get the out fence during the flushing buffer and then pass
> >>>> > it to SurfaceFlinger in eglSwapbuffer function.
> >>>> >
> >>>> Having a closer look it seems that the issue can be summarised as follows:
> >>>>  - flatland intercepts/interacts ANativeWindow::{de,}queueBuffer
> >>>> (how about
> >>>> ANativeWindow::cancelBuffer?)
> >>>>  - the program expects that a sync fd is available for both dequeue
> >>>> and queue
> >>>>
> >>>> At the same time:
> >>>>  - the ANativeWindow documentation does _not_ state such
> >>>> requirement
> >>>>  - even if it did, that will be somewhat wrong, since
> >>>> ANativeWindow::queueBuffer is called by eglSwapBuffers() Where the
> >>>> latter documentation clearly states - "... performs an implicit flush ...
> glFlush ...
> >>>> vgFlush"
> >>>>
> >>>> My take is that if flatland/Android framework does want an explicit
> >>>> sync point it should insert one with the EGL API.
> >>>> There could be alternative solutions, but the proposed patch seems
> >>>> wrong IMHO.
> >>>
> >>> In fact, I could work this around in producer
> >>> (Surface::queueBuffer) by ignoring the (-1) passed and by creating a sync
> using egl APIs. I see two problems with that.
> >>>
> >>> - Before getting a fd using eglDupNativeFenceFDANDROID(), you need a
> glFlush(),
> >>>    this costs additional cycles for each queueBuffer transaction on each
> BufferItem and
> >>>    I believe fd is also signaled due to this. (so I don’t know what we'll get by
> waiting on
> >>>    that fd on consumer side).
> >>> - AFAIK, the whole idea of explicit sync revolves around being able to pass
> fds created
> >>>   by driver between processes and this one breaks that chain. If we work this
> around in
> >>>   upper layers, explicit sync feature will have to be fixed for every other lib
> that may use
> >>>   lib mesa underneath.
> >>>
> >>> For these reasons, I still believe we should fix it here. Of course,
> >>> you and Rob have very valid points on cancelBuffer and about not
> >>> breaking gallium respectively, those need to be taken care of.
> >>>
> >> What I'm saying is - seems like the app/framework does something silly or at
> least undocumented.
> >> Fixing things in Mesa may be the right thing to do, but without more
> information, its everyone's guess who's got it wrong.
> >>
> >> As Rob asked earlier - can we get an a simple test case or some pseudo code
> illustrating the whole thing?
> >>
> >> Thanks
> >> Emil
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