Having the understanding of HZ, jiffies, and system timer, it is appropriate to discuss the implementation of time management. Most of the jobs in time management are handled by a dedicated function called timer handler. In Microblaze, the kernel registers timer_interrupt as the interrupt handler: irqreturn_t TIMER_TEXT timer_interrupt(int irq, void *dev_id) { timer_ack(); Read more…
Time management is crucial to Linux kernel. A massive of kernel functions are time-driven and therefore it is heavily dependent on time management. In Linux kernel, time management is handled by a piece of programmable hardware, known as system timer. The main job of system timer is to generate an Read more…
In LLVM system compiler, there is an option in the command command -mattr called target specific attributes. You may check each target attributes by using this command. llvm-as < /dev/null || llc -march=aemb -mattr=help note that -march=aemb is to select target architecture, in my case, aeMB. A list of attributes Read more…
Having the discussion of tick rate in my previous post, it is therefore appropriate to introduce jiffies in linux kernel. Jiffies is a global variable declared in <linux/jiffies.h> as: extern unsigned long volatile jiffies; Its only usage is to store the number of ticks occurred since system start-up. On kernel boot-up, jiffies is Read more…
For the past few weeks, I was given a task by my supervisor. The task sound simple, whenever there NOP (No operation) instruction will be use, LLVM should change it into XOR R0, R0, R0 which basically doing nothing since in aeMB, register zero (R0) always have zero values. NOP Read more…
With a large number of kernel functions are time-driven, the time management in kernel is very important. The frequency of the system timer (tick rate) is programmed on system boot based on a static preprocessor define, HZ. The value of HZ is architecture-dependent, and it is defined in: <asm/param.h>. The tick rate Read more…
I had officially completed my internship life in AESTE. Finishing my internship makes me wonders about my future. This feeling was never so intense. I never worried about my future so much before, when I was in my university. My supervisor told me that engineering is all about efficiency. He Read more…
Listen to one of the interns here talk a little about his internship experience at AESTE. The work we do is HARD – but fruitful. The working culture here is different – in a good way. You get to meet other interesting people – who will enrich you. An internship Read more…
Anyone who has a hobby would understand the satisfaction of completing something on which he or she enjoyed working. It doesn’t always look marketable, it doesn’t always look fashionable, it doesn’t always look picture-worthy. But it always looks good to the creator. Anyone who has a job would understand that Read more…
In the latest blog entry from one of our AESTE interns, he raised a couple of pertinent questions with regards to the very raison d’etre at AESTE. I thought that this might be an opportune time to address the issue. First, I shall address a very commonly held misconception – Read more…