CODEWITHSUNDEEP
c++linux-kernelkernel
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Reputation: 5467

Use kernel programming function in C++ program

I am a newbie in this area & am writing a C++/assembly code to benchmark (measure execution time) of a section of a code in clock cycles. I need to disable pre-emption and hard interrupts through my code. I know that linux kernel development permits use of preempt_disable(); &raw_local_irq_save(flags) functions to do the same.

My question is that I am not writing a kernel module, but a normal C/C++ program in user space. Can I use these system calls through my C++ code (i.e. from user space/ no kernel module?) Which header files should i include. if yes. Can someone please give me reading references or examples?

Thanks!!

Upvotes: 1

Views: 1368

Answers (2)

Nikolai Fetissov
Nikolai Fetissov

Reputation: 84159

You can't do this from userland application, especially disabling hardware interrupts, which provides the basis for many fundamental kernel functions like timekeeping.

What you can do instead is use sched_setscheduler(2) to set, say, SCHED_FIFO real-time priority, that is ask the kernel not to preempt your app until it voluntarily releases the CPU (usually a system call). Be careful though - you can easily lockup your system that way.

Upvotes: 2

cxxl
cxxl

Reputation: 5379

Usually that is impossible. The kernel will not let you block interrupts.

But assigning yourself a very high prio is usally good enough. Plus, make sure the benchmarked code runs long enough, e.g. by running it 10000 times in a loop. That way, some interrupts don't matter in the overall cycle counting. In my experience a code run time of 1 second is good enough (provided your system is not under heave stress) for home-brewn benchmarking.

Upvotes: 1

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