CODEWITHSUNDEEP
linuxlinux-kerneloperating-systemlinux-device-driversemaphore
Pravesh Gupta
Pravesh Gupta

Reputation: 101

Performace Evaluation between Semaphore and R/W Semaphore

I have been asked to write the test cases to show practically the performance of semaphore and read write semaphore in case of more readers and less writers and vice versa. I have implemented the semaphore (in kernel space we were asked actually) but not getting how to write the use cases and do a live practical evaluation ( categorically ) of same.

Upvotes: 0

Views: 217

Answers (2)

TheCodeArtist
TheCodeArtist

Reputation: 22477

Using your custom semaphores, write the following 2 C programs and compile them

  • reader.c
  • writer.c

As a simple rudimentary test, write a shell script test.sh and add your commands to load the test binaries as follows.

#!/bin/sh

./reader &
./reader &
./reader &
./reader &
./writer &

Launching the above shell script as ./test.sh will launch 4 readers and 1 writer. Customise this to your test scenario.

Ensure that your programs are operating properly i.e. verify data is being exchanged properly first before trying to profile the performance.

Once you are sure that IPC is working as expected, profile the cpu usage. Prior to launching test.sh, run the top command in another terminal. Observe the cpu usage patterns for varying number of readers/writers during the run-time of test script.

Also you can launch the individual binaries(or in the test-script) with :

  • time <binary>
    To print the total lifetime and time spent waiting on the kernel driver.

  • perf record <binary>
    and after completion, run perf annotate main
    To obtain the relative amount of time spent in various sections of the code.

Upvotes: 0

Matt
Matt

Reputation: 359

Why don't you just write your two versions of the code (Semaphore / R/W Semaphore) to start. The use cases will depend on the actual feature being tested. Is it a device driver? Is it IO related at all? Is it networking related? It's hard to come up with use cases without knowing this.

Generally what I would do for something like an IO benchmark would be running multiple simulations over an increasing memory footprint for a set of runs. Another set of runs might be over an increasing process load. Another may be over different block sizes. I would compare each one of those against something like aggregate bandwidth and see how performance (aggregate bandwidth in this case) changed over those tests.

Again, your use cases might be completely different if you are testing something like a USB driver.

Upvotes: 1

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