Re: What's a CPU second?
- From: DASDBill2@xxxxxxxxxxxx
- Date: 30 Mar 2007 09:10:38 -0700
In a message dated 3/30/2007 10:49:06 A.M. Central Daylight Time,
Gadam12@xxxxxxxxxxx writes:
the answer is that the MP effect is in the "hardware" (usingthe term loosely) operation of the CP(s) in coordinating the actions
that are largely invisibile to the operating system.
The MP effect occurs whenever software on any CP needs to access, or might
need to access in the near future (instruction pipeline look-ahead) any
hardware resource that might possibly be simultaneously changing due to any other
process within the LPAR. Examples of such hardware resources are bytes in real
storage, entries in a translation look-aside buffer, data in high-speed
cache, instructions in high-speed cache, or instructions in other CPs' pipelines.
And you can even suffer the MP effect with only one CP; e.g., if software
wants to access a byte that a concurrent I/O operation is changing, or
vice-versa, then one of the two accesses must wait until the other one completes.
Bill Fairchild
Plainfield, IL
************************************** See what's free at http://www.aol.com.
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