Linux scheduler Questions

From: Xin Tong
Date: Tue Nov 01 2011 - 08:24:30 EST


2 questions on Linux 2.6.x scheduler.

1. in Linux 2.6, when a process is waiting for IO. it will be placed
on the wait queue. is the wait queue per cpu or global ? I do not see
any field for the wait queue in the runqueue structure.
2. Linux 2.6 has the notion of scheduling domain, using an example to
explain what I am getting at here

In a HT enabled CPU, the CPU has 2 cores, each core has 2 threads.
there will be 2 levels of domain.
1. Domain of lev.1 ==> 2 groups, 1 physical core per group.
2. Domain of lev. 0 ==> 2 groups, 1 logical core per group.
When the load on the 2 logical cores is imbalanced, Linux will migrate
some jobs from one to another. What if there is an imbalance of
workload on the 2 physical cores ?

Thanks

Xin
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