Monitoring and Tuning the Linux Networking Stack: Sending Data - Packagecloud Blog

Monitoring and Tuning the Linux Networking Stack: Sending Data - Packagecloud Blog: "This blog post explains how computers running the Linux kernel send packets, as well as how to monitor and tune each component of the networking stack as packets flow from user programs to network hardware.

This post forms a pair with our previous post Monitoring and Tuning the Linux Networking Stack: Receiving Data."



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How To Code Like The Top Programmers At NASA — 10 Critical Rules

How To Code Like The Top Programmers At NASA — 10 Critical Rules: "NASA’s 10 rules for writing mission-critical code:

•  Restrict all code to very simple control flow constructs – do not use goto statements, setjmp or longjmp constructs, and direct or indirect recursion. 

• All loops must have a fixed upper-bound. It must be trivially possible for a checking tool to prove statically that a preset upper-bound on the number of iterations of a loop cannot be exceeded. If the loop-bound cannot be proven statically, the rule is considered violated.

• Do not use dynamic memory allocation after initialization. 

• No function should be longer than what can be printed on a single sheet of paper in a standard reference format with one line per statement and one line per declaration. Typically, this means no more than about 60 lines of code per function. 

• The assertion density of the code should average to a minimum of two assertions per function. Assertions are used to check for anomalous conditions that should never happen in real-life executions. Assertions must always be side-effect free and should be defined as Boolean tests. When an assertion fails, an explicit recovery action must be taken, e.g., by returning an error condition to the caller of the function that executes the failing assertion. Any assertion for which a static checking tool can prove that it can never fail or never hold violates this rule (I.e., it is not possible to satisfy the rule by adding unhelpful “assert(true)” statements). 

• Data objects must be declared at the smallest possible level of scope. 

• The return value of non-void functions must be checked by each calling function, and the validity of parameters must be checked inside each function. 

• The use of the preprocessor must be limited to the inclusion of header files and simple macro definitions. Token pasting, variable argument lists (ellipses), and recursive macro calls are not allowed. All macros must expand into complete syntactic units. The use of conditional compilation directives is often also dubious, but cannot always be avoided. This means that there should rarely be justification for more than one or two conditional compilation directives even in large software development efforts, beyond the standard boilerplate that avoids multiple inclusion of the same header file. Each such use should be flagged by a tool-based checker and justified in the code. 

• The use of pointers should be restricted. Specifically, no more than one level of dereferencing is allowed. Pointer dereference operations may not be hidden in macro definitions or inside typedef declarations. Function pointers are not permitted.
  All code must be compiled, from the first day of development, with all compiler warnings enabled at the compiler’s most pedantic setting. 

• All code must compile with these setting without any warnings. All code must be checked daily with at least one, but preferably more than one, state-of-the-art static source code analyzer and should pass the analyses with zero warnings."

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CompleteNewbiesClickHere - Linux Kernel Newbies

CompleteNewbiesClickHere - Linux Kernel Newbies: "First advice I got when I entered #kernelnewbies a year ago, was to download kernel version 0.0.1. It's a good start for someone who doesn't know jack about kernels, and wants to see a very basic one. [Dan Aloni]

[Sherilyn] The 0.01 kernel downloads to about 10000 lines of C and assembler, which is fairly manageable. Note that it's a barely functional UNIX with tons of bugs, but that doesn't stop it being useful if (like me) you just want to get a quick snapshot of the way in which a UNIX system boots up and starts executing processes, and a broad, uncluttered picture of the kernel system call API. I have written the following Wiki pages which may be of use as an introduction to kernel programming. Please add any corrections, etc."



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To become a good C programmer

To become a good C programmer: "Every once in a while I receive an email from a fellow programmer asking me what language I used for one of my games and how I learned it. Here is an entry that list the best things to read about C.
"



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Segfaults are our friends and teachers

Segfaults are our friends and teachers: "If you’ve written some C, you’ve almost certainly seen a segmentation fault at some point. I spent a long time thinking of it as a ‘thing that happens when you use pointers wrong in C’. That’s mostly true, but a segmentation fault actually has a very specific meaning. You get one when a process tries to access memory in a way that it’s not allowed to, or accessing invalid memory."



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Dan Luu: Recommended Programming blogs

Programming blogs: "Programming blogs
This is one of those “N technical things every programmer must read” lists, except that “programmer” is way too broad a term and the styles of writing people find helpful for them are too different for any such list to contain a non-zero number of items (if you want the entire list to be helpful to everyone). So here’s a list of some things you might want to read, and why you might (or might not) want to read them."



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A quick tutorial on implementing and debugging malloc, free, calloc, and realloc

A quick tutorial on implementing and debugging malloc, free, calloc, and realloc: "A quick tutorial on implementing and debugging malloc, free, calloc, and realloc
Let’s write a malloc and see how it works with existing programs!"



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C/C++ Links

Writing modern C++ servers using Wangle.

How to C in 2016
and then:
A critique of "How to C in 2016"