From: John Hunter <zhjwpku@gmail.com>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 6/8] drm/bochs: phase 3: provide a custom ->atomic_commit implementation
Date: Mon, 20 Jul 2015 07:56:36 +0800 [thread overview]
Message-ID: <CAEG8a3J2j+LmQLKf3zqnFxbOMNeP4eS8nk30hiMyUyAPA=47ww@mail.gmail.com> (raw)
In-Reply-To: <20150717090809.6c9d7d02@gmail.com>
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Hi Pekka,
Thanks for the information, I will talk to my mentor Daniel and try to find
out
what I can do about this.
Cheers,
Zhao Junwang
On Fri, Jul 17, 2015 at 2:08 PM, Pekka Paalanen <ppaalanen@gmail.com> wrote:
> On Thu, 16 Jul 2015 20:20:39 +0800
> John Hunter <zhjwpku@gmail.com> wrote:
>
> > From: Zhao Junwang <zhjwpku@gmail.com>
> >
> > This supports the asynchronous commits, required for page-flipping
> > Since it's virtual hw it's ok to commit async stuff right away, we
> > never have to wait for vblank.
>
> Hi,
>
> in theory, yes. This is what a patch to bochs implemented not too long
> ago, so AFAIK you are only replicating the existing behaviour.
>
> However, if userspace doing an async commit (or sync, I suppose) does
> not incur any waits in the kernel in e.g. sending the page flip event,
> then flip driven programs (e.g. a Wayland compositor, say, Weston)
> will be running its rendering loop as a busy-loop, because the kernel
> does not throttle it to the (virtual) display refresh rate.
>
> This will cause maximal CPU usage and poor user experience as
> everything else needs to fight for CPU time and event dispatch to get
> through, like input.
>
> I would hope someone could do a follow-up to implement a refresh cycle
> emulation based on a clock. Userspace expects page flips to happen at
> most at refresh rate when asking for vblank-synced flips. It's only
> natural for userspace to drive its rendering loop based on the vblank
> cycle.
>
>
> Thanks,
> pq
>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Signed-off-by: Zhao Junwang <zhjwpku@gmail.com>
> > ---
> > drivers/gpu/drm/bochs/bochs_mm.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bochs/bochs_mm.c
> b/drivers/gpu/drm/bochs/bochs_mm.c
> > index c1d819c..37ac2ca 100644
> > --- a/drivers/gpu/drm/bochs/bochs_mm.c
> > +++ b/drivers/gpu/drm/bochs/bochs_mm.c
> > @@ -545,8 +545,15 @@ bochs_user_framebuffer_create(struct drm_device
> *dev,
> > return &bochs_fb->base;
> > }
> >
> > +static int bochs_atomic_commit(struct drm_device *dev,
> > + struct drm_atomic_state *a,
> > + bool async)
> > +{
> > + return drm_atomic_helper_commit(dev, a, false);
> > +}
> > +
> > const struct drm_mode_config_funcs bochs_mode_funcs = {
> > .fb_create = bochs_user_framebuffer_create,
> > .atomic_check = drm_atomic_helper_check,
> > - .atomic_commit = drm_atomic_helper_commit,
> > + .atomic_commit = bochs_atomic_commit,
> > };
>
>
--
Best regards
Junwang Zhao
Microprocessor Research and Develop Center
Department of Computer Science &Technology
Peking University
Beijing, 100871, PRC
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next prev parent reply other threads:[~2015-07-19 23:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 12:20 [PATCH 0/8] drm/bochs: convert bochs to atomic mode-setting John Hunter
2015-07-16 12:20 ` [PATCH 1/8] drm/bochs: phase 1 - use the transitional helpers John Hunter
2015-07-16 15:49 ` Gerd Hoffmann
2015-07-16 18:22 ` Daniel Vetter
2015-07-16 12:20 ` [PATCH 2/8] drm/bochs: phase 2: wire up state reset(), duplicate() and destroy John Hunter
2015-07-16 12:20 ` [PATCH 3/8] drm/bochs: stop looking at legacy state John Hunter
2015-07-16 12:20 ` [PATCH 4/8] drm/bochs: phase 3: for plane updates: switch to atomic helper internally John Hunter
2015-07-16 12:20 ` [PATCH 5/8] drm/bochs: phase 3: use atomic .set_config helper John Hunter
2015-07-16 12:20 ` [PATCH 6/8] drm/bochs: phase 3: provide a custom ->atomic_commit implementation John Hunter
2015-07-17 6:08 ` Pekka Paalanen
2015-07-19 23:56 ` John Hunter [this message]
2015-07-20 0:20 ` Stéphane Marchesin
2015-07-20 7:46 ` Pekka Paalanen
2015-07-20 8:58 ` Stéphane Marchesin
2015-07-20 9:35 ` KMS timings (Re: [PATCH 6/8] drm/bochs: phase 3: provide a custom ->atomic_commit implementation) Pekka Paalanen
2015-07-20 14:21 ` Daniel Vetter
2015-07-20 17:32 ` Stéphane Marchesin
2015-07-21 7:06 ` Pekka Paalanen
2015-07-21 9:02 ` Daniel Vetter
2015-07-21 11:22 ` Pekka Paalanen
2015-07-21 13:47 ` Daniel Vetter
2015-07-16 12:20 ` [PATCH 7/8] drm/bochs: phase 3: switch to drm_atomic_helper_page_flip John Hunter
2015-07-16 12:20 ` [PATCH 8/8] drm/bochs: atomic dpms support John Hunter
2016-03-02 10:13 ` [PATCH 0/8] drm/bochs: convert bochs to atomic mode-setting Emil Velikov
2016-03-02 15:38 ` Gerd Hoffmann
2016-03-02 18:02 ` Emil Velikov
2016-03-03 9:28 ` Gerd Hoffmann
2016-03-04 8:31 ` John Hunter
2016-03-04 14:05 ` Emil Velikov
2016-03-07 9:34 ` Gerd Hoffmann
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