Re: [Coremu-list-devel] PIT frequency expression

[zhaoguo w. <tig...@gm...>]

Ching-Tsun:

     Sorry for the delay. The general purpose of this expression is to
reduce the PIT frequency when the number of emulated cores is
much large than the number of the physical cores on the host machine.
Then we can avoid large number of signals when emulate large number
of cores. However, this expression is a little curious-looking because
we use linear fitting method based on the data profiled on our environment,
a four core machine and a 4X4 core machine.

At last, I believe this method must can be approved to reduce PIT more
efficiently. :-)

2011/10/30 Ching-Tsun Chou <chi...@gm...>:
> In qemu/cm-timer.c, there is an expression for setting cm_pit_freq, which is
> aliased to PIT_FREQ:
> void cm_init_pit_freq(void)
> {
>     double v_num = coremu_get_targetcpu();
>     double p_num = coremu_get_hostcpu();
>     double p_root = sqrt(p_num) / 4;
>     double suggest = p_root * pow(v_num / p_num, p_root);
>     int pit_freq_suggest = ceil(suggest);
>     cm_pit_freq = 1193182 / pit_freq_suggest;
> }
> Could someone explain what is the rationale behind this curious-looking
> expression?
> Thanks in advance!
> - Ching Tsun
> ------------------------------------------------------------------------------
> Get your Android app more play: Bring it to the BlackBerry PlayBook
> in minutes. BlackBerry App World&#153; now supports Android&#153; Apps
> for the BlackBerry&reg; PlayBook&#153;. Discover just how easy and simple
> it is! http://p.sf.net/sfu/android-dev2dev
>
> _______________________________________________
> Coremu-list-devel mailing list
> Cor...@li...
> https://lists.sourceforge.net/lists/listinfo/coremu-list-devel
>
>



-- 
Zhaoguo Wang, Parallel Processing Institute, Fudan University

Address: Room 320, Software Building, 825 Zhangheng Road, Shanghai, China

tig...@gm...
http://ppi.fudan.edu.cn/zhaoguo_wang