From: "Keith Packard" <keithp@keithp.com>
To: Lionel Landwerlin <lionel.g.landwerlin@intel.com>,
Dylan Baker <dylan@pnwbakers.com>,
mesa-dev@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 6/7] vulkan: Add new VK_MESA_query_timestamp extension
Date: Tue, 13 Feb 2018 13:11:25 -0800 [thread overview]
Message-ID: <87inb0a936.fsf@keithp.com> (raw)
In-Reply-To: <4a9ad7ce-b5af-b498-8816-6fcfb4009991@intel.com>
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Lionel Landwerlin <lionel.g.landwerlin@intel.com> writes:
> I'm assuming the correlation is done outside the vulkan driver? With a
> clock_gettime() maybe?
>
> If that's the case, I'm afraid this will be highly inaccurate.
> The kernel might execute other tasks when the ioctl() happens and that
> might introduce (in my experience) a few milliseconds of delay.
Yes, I agree. The trouble is that the window system layer works in one
time base while the rendering layer works in the other, so there's no
one driver which has access to both values, at least in Mesa.
> I think if you want to do something like that, this has to be
> implemented in the kernel, making sure you disable interruptions while
> doing the correlation.
That was my thinking originally, until I realized that there wasn't a
single place which knew of the two clocks.
Suggestions are welcome; I just don't know how the rendering driver is
supposed to know what timebase the window system is running in?
--
-keith
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next prev parent reply other threads:[~2018-02-13 21:11 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-10 4:45 [PATCH 0/7] vulkan: Add direct display extensions Keith Packard
2018-02-10 4:45 ` [PATCH 1/7] vulkan: Add KHR_display extension to anv and radv using DRM Keith Packard
2018-02-12 15:27 ` Eric Engestrom
2018-02-12 22:16 ` Keith Packard
2018-02-12 16:18 ` [Mesa-dev] " Emil Velikov
2018-02-12 23:12 ` Keith Packard
2018-02-14 1:10 ` Jason Ekstrand
2018-02-15 17:46 ` Keith Packard
2018-02-23 23:00 ` Jason Ekstrand
2018-02-23 23:43 ` Keith Packard
2018-02-24 0:51 ` Jason Ekstrand
2018-03-12 23:02 ` Keith Packard
2018-03-29 6:59 ` Mao, David
2018-03-29 15:05 ` Keith Packard
2018-02-10 4:45 ` [PATCH 2/7] vulkan: Add EXT_direct_mode_display Keith Packard
2018-02-10 4:45 ` [PATCH 3/7] vulkan: Add EXT_acquire_xlib_display Keith Packard
2018-02-13 0:16 ` Dylan Baker
2018-02-10 4:45 ` [PATCH 4/7] vulkan: Add VK_EXT_display_surface_counter [v4] Keith Packard
2018-02-10 4:45 ` [PATCH 5/7] vulkan: add VK_EXT_display_control [v4] Keith Packard
2018-02-10 4:45 ` [PATCH 6/7] vulkan: Add new VK_MESA_query_timestamp extension Keith Packard
2018-02-13 0:20 ` Dylan Baker
2018-02-13 10:49 ` [Mesa-dev] " Lionel Landwerlin
2018-02-13 21:11 ` Keith Packard [this message]
2018-02-10 4:45 ` [PATCH 7/7] vulkan: Add VK_GOOGLE_display_timing extension (x11 and display backends) Keith Packard
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