What is Linux Napi?

New API (also referred to as NAPI) is an interface to use interrupt mitigation techniques for networking devices in the Linux kernel. Such an approach is intended to reduce the overhead of packet receiving.

What is SoftIrq in Linux?

SoftIrqs allow the critical part of servicing hardware interrupts to be as short as possible; instead of having to process the entire hw interrupt on the spot, the important data is read off the device into RAM or otherwise, and then a SoftIrq is started to finish the work.

What is difference between Softirq and Tasklet?

Generally speaking, softirqs are re-entrant functions and must explicitly protect their data structures with spin locks. Tasklets differ from softirqs because a tasklet is always serialized with respect to itself; in other words, a tasklet cannot be executed by two CPUs at the same time.

Can Softirq be interrupted?

Softirqs run at a high priority (though with an interesting exception, described below), but with hardware interrupts enabled. They thus will normally preempt any work except the response to a “real” hardware interrupt.

Can Tasklet be preempted?

Since preemption is “disabled”, even though kernel context holds “spin_lock”, tasklet cannot preempt the kernel context which is calling ioctl and this kernel context is kind of “safe” from BH.

Can Softirq be preempted?

The bottom two can preempt each other, but above that is a strict hierarchy: each can only be preempted by the ones above it. For example, while a softirq is running on a CPU, no other softirq will preempt it, but a hardware interrupt can. However, any other CPUs in the system execute independently.

What is the difference between Workqueue and Tasklet?

Workqueue functions run in the context of a kernel process, but tasklet functions run in the software interrupt context. This means that workqueue functions must not be atomic as tasklet functions. Tasklets always run on the processor from which they were originally submitted.

Can Printk’s be used in interrupt context?

It does work. printk is designed to be called from interrupt or process context. If it wasn’t, it wouldn’t be much use for debugging. You obviously don’t call it in interrupt context in a production driver, though.

What is Linux Tasklet?

Tasklet in Linux Kernel Tasklets are used to queue up work to be done at a later time. Tasklets can be run in parallel, but the same tasklet cannot be run on multiple CPUs at the same time. Also, each tasklet will run only on the CPU that schedules it, to optimize cache usage.

What is the difference between printf and printk?

Difference between Printk() and Printf() in Linux : printf() is a C Standard Library function. printk() is used by the kernel to print. To print something from the application layer it uses printf(). The printk() method can be called at any time from almost anywhere in the kernel.

What library is printk in?

It acts as a debugging tool for kernel programmers who need this function for logging messages from the kernel. The printk function prototype is: int printk(const char *fmt.); C standard library and its printf function is unavailable in kernel mode, hence the need for printk .

What is difference between Tasklet and Workqueue?