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List: kwin
Subject: Re: Review Request 109784: rebase measuring to nano resolution and fix initial padding
From: Thomas_Lübking <thomas.luebking () gmail ! com>
Date: 2013-04-01 13:11:47
Message-ID: 20130401131147.31016.61476 () vidsolbach ! de
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> On April 1, 2013, 9:13 a.m., Martin Gräßlin wrote:
> > do you know how that will behave on systems which do not provide high precision \
> > timers? And how likely it is that a user doesn't have such a timer?
Looked up Qt implementations for Win/Mac/Symbian - they operate on the cpu ticks (and \
for Symbian blow up µsecs) Afair WinVista+ require HPET HW, so that implementation \
could be specialized and get better precision (i would not trust esp. the Win&Mac \
implementations reg. speedstepâ„¢)
Any tick implementation will get you µsec precision (at best) up to 1GHz (and mili \
below 1MHz) - so with HPET (since 2005, 10MHz at least) or on even modern ARM \
architectures or modern CPUs and tick based calculation (and not linux, probably not \
even bsd) I would not expect realy nano, but only micro resolution.
Luckily that's absolutely sufficient for our purposes, but QElapsedTimer gets you \
either mili or nano.
tl;dr - it won't get worse.
(Since we cannot "sleep" micro or nanoseconds with the render QTimer, we'll btw. \
always end up between 58.8 and 62.5 FPS)
- Thomas
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/109784/#review30199
-----------------------------------------------------------
On March 30, 2013, 5:40 p.m., Thomas Lübking wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://git.reviewboard.kde.org/r/109784/
> -----------------------------------------------------------
>
> (Updated March 30, 2013, 5:40 p.m.)
>
>
> Review request for kwin, Martin Gräßlin and Ralf Jung.
>
>
> Description
> -------
>
> summarized
>
>
> Diffs
> -----
>
> kwin/composite.h ebaf7e7
> kwin/composite.cpp ee885dc
> kwin/options.h f61a66f
> kwin/options.cpp 6abd3f0
> kwin/scene.h 5d49c40
> kwin/scene_opengl.h 409ec3d
> kwin/scene_opengl.cpp 3343164
> kwin/scene_xrender.h 4a93940
> kwin/scene_xrender.cpp ab90815
>
> Diff: http://git.reviewboard.kde.org/r/109784/diff/
>
>
> Testing
> -------
>
> it's math.
> fpsinterval is n*vblankTime so this moves it 1ms past the last assumed tick before \
> the wanted interval spot, so that we don't have to fear to miss it.
> Assuming we paint every 3rd frame:
>
> A 1 2 3 4 5 - B 1 2 3 4 5 - C 1 2 3 4 5 - A
> ^ here (C1)
>
>
> Thanks,
>
> Thomas Lübking
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="http://git.reviewboard.kde.org/r/109784/">http://git.reviewboard.kde.org/r/109784/</a>
</td>
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<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On April 1st, 2013, 9:13 a.m. UTC, <b>Martin \
Gräßlin</b> wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;"> <pre style="white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">do you know how that will behave on systems which do not provide high \
precision timers? And how likely it is that a user doesn't have such a \
timer?</pre> </blockquote>
</blockquote>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Looked up Qt \
implementations for Win/Mac/Symbian - they operate on the cpu ticks (and for Symbian \
blow up µsecs) Afair WinVista+ require HPET HW, so that implementation could be \
specialized and get better precision (i would not trust esp. the Win&Mac \
implementations reg. speedstepâ„¢)
Any tick implementation will get you µsec precision (at best) up to 1GHz (and mili \
below 1MHz) - so with HPET (since 2005, 10MHz at least) or on even modern ARM \
architectures or modern CPUs and tick based calculation (and not linux, probably not \
even bsd) I would not expect realy nano, but only micro resolution.
Luckily that's absolutely sufficient for our purposes, but QElapsedTimer gets you \
either mili or nano.
tl;dr - it won't get worse.
(Since we cannot "sleep" micro or nanoseconds with the render QTimer, \
we'll btw. always end up between 58.8 and 62.5 FPS)</pre> <br />
<p>- Thomas</p>
<br />
<p>On March 30th, 2013, 5:40 p.m. UTC, Thomas Lübking wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" \
style="background-image: \
url('http://git.reviewboard.kde.org/static/rb/images/review_request_box_top_bg.ab6f3b1072c9.png'); \
background-position: left top; background-repeat: repeat-x; border: 1px black \
solid;"> <tr>
<td>
<div>Review request for kwin, Martin Gräßlin and Ralf Jung.</div>
<div>By Thomas Lübking.</div>
<p style="color: grey;"><i>Updated March 30, 2013, 5:40 p.m.</i></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">summarized</pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">it's math. fpsinterval is n*vblankTime so this moves it 1ms past the \
last assumed tick before the wanted interval spot, so that we don't have to fear \
to miss it.
Assuming we paint every 3rd frame:
A 1 2 3 4 5 - B 1 2 3 4 5 - C 1 2 3 4 5 - A
^ here (C1)</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>kwin/composite.h <span style="color: grey">(ebaf7e7)</span></li>
<li>kwin/composite.cpp <span style="color: grey">(ee885dc)</span></li>
<li>kwin/options.h <span style="color: grey">(f61a66f)</span></li>
<li>kwin/options.cpp <span style="color: grey">(6abd3f0)</span></li>
<li>kwin/scene.h <span style="color: grey">(5d49c40)</span></li>
<li>kwin/scene_opengl.h <span style="color: grey">(409ec3d)</span></li>
<li>kwin/scene_opengl.cpp <span style="color: grey">(3343164)</span></li>
<li>kwin/scene_xrender.h <span style="color: grey">(4a93940)</span></li>
<li>kwin/scene_xrender.cpp <span style="color: grey">(ab90815)</span></li>
</ul>
<p><a href="http://git.reviewboard.kde.org/r/109784/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>
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