Messages in this thread |  | | | From | (Larry McVoy) | | Subject | Re: context switch time | | Date | Wed, 15 Apr 1998 14:39:26 -0600 |
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: Could someone knowledged enough please tell me approximately how many : cycles takes a process context switch on a pentium in Linux?
It depends. If all you want is the 2 process flipping back and forth number, it is ~5 usecs on a K6@233Mhz and ~9 usecs on P5@120Mhz. The numbers go up dramatically as the size of the process goes up. By orders of magnitude. Think about it: if all I am dong is context switching then most of what I need is in the L2 cache tagged by context id and I don't go to memory at all. So it becomes a pure CPU speed issue. But if I'm touching data in each context, then I am throwing the other guy's data out of the cache and he gets stalled when he sarts up again.
Unfortunately, the latter is far more common than the former.
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