linux kernel - What is the overhead involved in a mode switch -

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Many times I have read / heard that the disabling of many calls etc. will be disabled because the apps make a mode The switch goes from user mode to kernel mode and after a system call execution, a mode switch starts after re-implementing in user mode.

My question is, is there a mode switch overhead? Does the CPU cache become invalid or TLB entries come out or what is the reason for this?

Please note that I am asking about overhead involved in mode switch and do not have context switches. I know that mode switch and reference switch are two different things and I am fully aware of the overhead associated with the reference switch, but I am unable to understand what is the cause of the overhead due to a mode switch?

If it is possible, please give some information about any special Nix platform like Linux, Free BSD, Solaris etc

Regards

Redness

There should be no CPU cache or TLB flush on the simple mode switch.

A quick test tells me that, on my Linux laptop, this 0.12 microscope does a simple process for a userspace process to complete, which is a bit of work apart from the kernel mode and back of the switch Gives the amount. I am using getuid (), which only copy an integer from an in-memory structure, I stress confirms that syscall is repeated over MAX. 

  #include & lt; Unistd.h & gt; # Maximum 100000000 int main () {int ii; For (ii = 0; ii

This takes approximately 11 seconds on my laptop, which is used by using time ./testover , and 11 seconds divided by 100 million It gives you 0.11 microseconds.

Technically, it has two mode switches, so I think you can claim that a mode switch takes 0.055 microseconds, but one-way switch is not very useful, so I To make the back number more relevant.


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