If you have a limit on the number of modbus clients then dropping old connections when a new one arrives is actually suggested in the modbus implementation guide (https://www.modbus.org/docs/Modbus_Messaging_Implementation_Guide_V1_0b.pdf) Nevertheless a mechanism must be implemented in case of exceeding the number of authorized connection. In such a case we recommend to close the oldest unused … Read more
I think you can find a lot of documentation about the kmalloc + mmap part. However, I am not sure that you can kmalloc so much memory in a contiguous way, and have it always at the same place. Sure, if everything is always the same, then you might get a constant address. However, each … Read more
Look here for a good wiki book. I had some coursework I wrote when I was teaching Electronic Eng, but I couldn’t find it around. When I was teaching, most of the students were happy to use the schematic capture tools in the Xilinx Foundation package. They’ve moved onto ISE and WebPACK now. You can … Read more
Integer Square Roots by Jack W. Crenshaw could be useful as another reference. The C Snippets Archive also has an integer square root implementation. This one goes beyond just the integer result, and calculates extra fractional (fixed-point) bits of the answer. (Update: unfortunately, the C snippets archive is now defunct. The link points to the … Read more
You can use the _alloca function. I believe that it’s not exactly Standard, but as far as I know, nearly all common compilers implement it. When you use it as a default argument, it allocates off the caller’s stack. // Header typedef struct {} something; size_t get_size(); something* create_something(void* mem); // Usage something* ptr = … Read more
In terms of performance, my understanding is that exceptions actually reduce the size and increase the performance of the normal execution paths of code, but make the exceptional/error paths more expensive. (often a lot more expensive). So if your only concern is performance, I would say don’t worry about later. If today’s CPU can handle … Read more
The most common way to determine the deepest stack usage is to initialize the stack memory with some known but unusual value, then periodically (or at the end of a big test run) see where that pattern stops. This is exactly how the IAR IDE determines the amount of stack used.
GCC docs : -fstack-usage Makes the compiler output stack usage information for the program, on a per-function basis. The filename for the dump is made by appending .su to the auxname. auxname is generated from the name of the output file, if explicitly specified and it is not an executable, otherwise it is the basename … Read more
As Jason C points out in the comments, the version you posted is most likely the best choice, due to its superior precision near the edge cases: float lerp(float a, float b, float f) { return a * (1.0 – f) + (b * f); } If we disregard from precision for a while, we … Read more
Two issues here: Whether and when keeping certain fields together is an optimization. How to do actually do it. The reason that it might help, is that memory is loaded into the CPU cache in chunks called “cache lines”. This takes time, and generally speaking the more cache lines loaded for your object, the longer … Read more