linux-kernel - Re: [PATCH] Psychovisually-optimized HZ setting (2.6.33.3)

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Message-ID: <29999.1272405003@localhost>
Date:	Tue, 27 Apr 2010 17:50:03 -0400
From:	Valdis.Kletnieks@...edu
To:	Uwaysi Bin Kareem <uwaysi.bin.kareem@...adoxuncreated.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Psychovisually-optimized HZ setting (2.6.33.3)

On Tue, 27 Apr 2010 21:03:11 +0200, Uwaysi Bin Kareem said:

> http://www.paradoxuncreated.com/articles/Millennium/Millennium.html

> +	config HZ_3956
> +		bool "3956 HZ"
> +	help
> +	 3956 Hz is nearly the highest timer interrupt rate supported in the kernel.
> +	 Graphics workstations, and OpenGL applications may benefit from this,
> +	 since it gives the lowest framerate-jitter. The exact value 3956 is
> +	 psychovisually-optimized, meaning that it aims for a level of jitter,

Even after reading your link, it's unclear why 3956 and not 4000. All your link
said was "A granularity below 0.5 milliseconds, seems to suit the human
senses." - anything over 2000 meets that requirement.  Also, if your screen
refresh is sitting at 72hz or a bit under 14ms per refresh, any jitter under
that won't really matter much - it doesn't matter if your next frame is
ready 5ms early or 5.5ms early, you *still* have to wait for the next vertical
blanking interval or suffer tearing.

There's also the case of programs where HZ=300 would *make* the time budget,
but the added 3,356 timer interrupts and associated overhead would cause a
missed screen refresh.

I think you need more technical justification of why 3956 is better than 1000.

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