In other words, putting the data that gettimeofday needs into the address-space of every process costs just as many bytes now as it always did well, modulus avg number of processess on a box , but the available memory increases exponentially. With Safari, you learn the way you learn best. The amount of memory available increases a lot more than the available syscalls do. For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. How to Measure Time to execute a function in Kernel space. The time and gettimeofday System Calls. The time now is

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You are currently viewing LQ as a guest. I have no access to the usual time functions in the standard library because I am in kernel space.

Then the libc can just fetch the relevant data from its own address space and incur no context switch overhead. Click Here to receive this Complete Guide absolutely free. Join our community today! Find More Posts by barunparichha. A patch of this nature was discussed a few years ago, but I’m not sure if any code resulted.

For kernel space following code will work Introduction to Linux – A Hands on Guide Getgimeofday guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter. Here is an example program that shows usage: Of course it’s possible that the effect would be kernell dramatic on x86 hardware running Linux but it’s still an option to consider.


gettimeofday(2) – Linux manual page

The time system call is superseded by gettimeofdaybut it is still included in Linux for backward compatibility. Posted Aug 23, With Safari, you learn the way you learn best.

The system call would still exist for legacy support Post as a guest Name. The code in user space is as below. This is, of course, a standard memory for speed trade-off.

As a first version, I therefore check if the current hour is between start and end, which are set via parameters to the module. Stack Overflow works best with JavaScript enabled. Tridge of Samba fame once described to me a case on some system where he tweaked a kernel and libc in this way and saw a significant performance improvement kernek Fujitsu hardware?

Just doing a strace on date executable gives us an idea to get the current date in the kernel mode. Because clock can’t give accracy in msec. Open Source Consulting Domain Registration. Please visit this page to clear all LQ-related cookies. Visit the following links: Returns getitmeofday number of elapsed seconds since midnight at the start of January 1, UTC.


gettimeofday() — user-space vs. system call

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Comparing Linux and Minix While gettimeofday should be one of the simplest system calls in the universe and uname should be another I’m writing a kernel module that checks to see if the time is between two specified hours, gettimeofay disables input if it is. Start Free Trial No credit card required.

Understanding the Linux Kernel, 3rd Edition by Marco Cesati, Daniel P. Bovet

Having a problem installing a new program? By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. How to measure the time to build a package? I need to measure time in kernel space not in user space.