Tomas Hruby 6aa26565e6 SMP - Big kernel lock (BKL) ...

- to isolate execution inside kernel we use a big kernel lock
  implemented as a spinlock

- the lock is acquired asap after entering kernel mode and released as
  late as possible. Only one CPU as a time can execute the core kernel
  code

- measurement son real hw show that the overhead of this lock is close
  to 0% of kernel time for the currnet system

- the overhead of this lock may be as high as 45% of kernel time in
  virtual machines depending on the ratio between physical CPUs
  available and emulated CPUs. The performance degradation is
  significant

2010-09-15 14:10:03 +00:00

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