Along the lines of what I mentioned in this post. I recommend you use the SIGAR API. I use the SIGAR API in one of my own applications and it is great. You’ll find it is stable, well supported, and full of useful examples. It is open-source with a GPL 2 Apache 2.0 license. Check … Read more
You got some of these right, but whoever wrote the questions tricked you on at least one question: global variables ——-> data (correct) static variables ——-> data (correct) constant data types —–> code and/or data. Consider string literals for a situation when a constant itself would be stored in the data segment, and references to … Read more
A static two-dimensional array looks like an array of arrays – it’s just laid out contiguously in memory. Arrays are not the same thing as pointers, but because you can often use them pretty much interchangeably it can get confusing sometimes. The compiler keeps track properly, though, which makes everything line up nicely. You do … Read more
Numbers everyone should know 0.5 ns – CPU L1 dCACHE reference 1 ns – speed-of-light (a photon) travel a 1 ft (30.5cm) distance 5 ns – CPU L1 iCACHE Branch mispredict 7 ns – CPU L2 CACHE reference 71 ns – CPU cross-QPI/NUMA best case on XEON E5-46* 100 ns – MUTEX lock/unlock 100 ns … Read more
If the cache line containing the byte or word you’re loading is not already present in the cache, your CPU will request the 64 bytes that begin at the cache line boundary (the largest address below the one you need that is multiple of 64). Modern PC memory modules transfer 64 bits (8 bytes) at … Read more
Each Java process has a pid, which you first need to find with the jps command. Once you have the pid, you can use jstat -gc [insert-pid-here] to find statistics of the behavior of the garbage collected heap. jstat -gccapacity [insert-pid-here] will present information about memory pool generation and space capabilities. jstat -gcutil [insert-pid-here] will … Read more
“Old space” is the biggest and most configurable section of V8’s managed (aka garbage-collected) heap (i.e. where the JavaScript objects live), and the –max-old-space-size flag controls its maximum size. As memory consumption approaches the limit, V8 will spend more time on garbage collection in an effort to free unused memory. If heap memory consumption (i.e. … Read more
Upon comparing test code with Sam, I determined that we are both right! However, about different things: Accessing memory (reading and writing) is just as fast wherever it is – stack, global or heap. Allocating it, however, is fastest on stack and slowest on heap. It goes like this: stack < global < heap. (allocation … Read more
As far as the ISO C standard (the official definition of the language) is concerned, accessing an array outside its bounds has “undefined behavior“. The literal meaning of this is: behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements A non-normative note … Read more