Re: The values of gettimeofday() jumps.

[P@draigBrady.com]

Liangchen Zheng wrote:
> Hello,
> 	We have several SMP machines (Tyan Tiger MPX motherboard, 2
> AthlonMP 1900+ CPU, linux-2.4.21-20.EL).  When running some time
> sensitive programs, I observed that the values of gettimeofday() jumped
> sometimes on a couple of machines (other machines are fine), from
> several hundreds milliseconds to a couple of seconds.

That sounds like what I described here:
http://lkml.org/lkml/2005/4/4/57

2 options as far as I can see.

1. Use irq affinity to bind the timer irq to a particular CPU,
   while using CPU affinity to bind your process to a particular CPU.

2. Change the code to maintain a last_tsc_low for each CPU.

--
Pádraig Brady - http://www.pixelbeat.org
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