Prev: sound/core/timer.c: inconsistent lock state reported for tu->qlock
Next: [PATCH] logfs: kill BKL
From: Randy Dunlap on 27 Apr 2010 16:00
On Tue, 27 Apr 2010 21:03:11 +0200 Uwaysi Bin Kareem wrote:

> This is based on the research I did with optimizing my machine for
> graphics.
> I also wrote the following article:
> http://www.paradoxuncreated.com/articles/Millennium/Millennium.html
> It is a bit outdated now, but I will update it with current information.
> The value might iterate.

Hi,

What CPU architectures or platforms did you test this on?
Were any other kernel changes needed?


> Peace Be With You,
> Uwaysi Bin Kareem.
>
>
> --- Kconfig.hzorig 2010-04-27 13:33:10.302162524 +0200
> +++ Kconfig.hz 2010-04-27 20:39:54.736959816 +0200
> @@ -45,6 +45,18 @@
> 1000 Hz is the preferred choice for desktop systems and other
> systems requiring fast interactive responses to events.
>
> + 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,

drop first comma.

> + since it gives the lowest framerate-jitter. The exact value 3956 is
> + psychovisually-optimized, meaning that it aims for a level of jitter,
> + percieved to be natural, and therefore non-nosiy. It is tuned for a

perceived non-noisy.

> + profile of "where the human senses register the most information".
> +
> +
> +
> endchoice
>
> config HZ
> @@ -53,6 +65,7 @@
> default 250 if HZ_250
> default 300 if HZ_300
> default 1000 if HZ_1000
> + default 3956 if HZ_3956
>
> config SCHED_HRTICK
> def_bool HIGH_RES_TIMERS && (!SMP || USE_GENERIC_SMP_HELPERS)
>
> --


---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
From: Valdis.Kletnieks on 27 Apr 2010 18:00
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.
 | 
Pages: 1
Prev: sound/core/timer.c: inconsistent lock state reported for tu->qlock
Next: [PATCH] logfs: kill BKL