Re: [Gems-users] Simulated machine execution time


Date: Tue, 23 Oct 2007 15:50:34 -0500
From: Mike Marty <mikem@xxxxxxxxxxx>
Subject: Re: [Gems-users] Simulated machine execution time
I was wondering if the frequency of clock-based interrupts could impact the scheduling of various OS events (like cross-calls, TLB shootdowns, etc) and even the scheduling of application threads. I'm not really an OS guy, so I'm not sure. But this is what I had in mind

--Mike


Greg Byrd wrote:
Agreed. Clock-based interrupts will occur less frequently (i.e., more cycles in between). I/O timing will look different. Are there other differences that you've encountered that I haven't considered? (This isn't a rhetorical question -- I'm really interested in what others think about this.)

...Greg


Mike Marty wrote:
>> I tend to use the "sarek" configuration. In >> $SIMICS/home/sarek/sarek-common.simics, there's a python variable "cpu_freq" >> that sets this parameter. It defaults to 75.
>>
>> Also, at least for the Ultrasparc processor, it's saved when you do a simics >> checkpoint. Look for the string "freq_mhz". You can just change this (for all >> processors) in the checkpoint file directly.
>>
>> Note that changing this only affects time from the Simics point of view. It >> doesn't have any effect on Ruby cycles.
>>
>> >> > Except that it could change the execution path that a program takes
>
> --mike
>
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