CODEWITHSUNDEEP
linuxperformancestatisticslinux-kernel
Łukasz Sowa
Łukasz Sowa

Reputation: 1287

Accurate way of measuring overhead in kernel space

I recently implemented a security mechanism for Linux which hooks into system calls. Now I have to measure the overhead caused by it. The project requires to compare the execution time of typical Linux apps with and without the mechanism. By typical Linux apps I assume ex. gzipping 1G file, doing 'find /', grepping files. The main goal is to show the overhead in different types of tasks: CPU bound, I/O bound etc.

The question is: how to organise the test so that they will be reliable? The first important thing is the fact that my mechanism works only in kernel space, so it is relevant to compare systime. I can use 'time' command for it, but is it the most accurate way of measuring systime? Another idea is to run those apps in long loops to minimize error. Then the loops should be inside or outside time command? If they are outside I will get many results - should I choose min, max, median, average?

Thanks for any suggestions.

Upvotes: 4

Views: 922

Answers (1)

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

I think you want more to measure a typical application payload (as Ninjajl's comment suggests, the compilation of the kernel could be a good payload). You probably don't want to measure the overhead inside each syscall itself, or even inside the kernel as a whole.

The reason for this is that most applications spend much more time and resource in user-space than in kernel-land (i.e. syscalls), so overhead inside syscalls is a "second-order" effect and probably don't matter as much. Of course, there are probable exceptions.

Perhaps phoronix test suite might be relevant.

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Upvotes: 3

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