3 ms·

Zeroing memory is certainly not free, and if you're doing some types of real-time applications, can have a significant cost. http://randomascii.wordpress.com/2

Zeroing memory is certainly not free, and if you're doing some types of real-time applications, can have a significant cost. http://randomascii.wordpress.com/2014/12/10/hidden-costs-of-memory-allocation/ http://randomascii.wordpress.com/2014/12/10/hidden-costs-of-...

pkolaczk 12y ago
If the compiler could prove you never read an array element before writing (like it is most of the time in Java, and should be all of the time in C), it could optimize the entire zeroing step away. Java does this very often. And initializing your variables close to the point of declaring them is a good practice in C anyways, which should make it easy for the compiler to analyze.
ArkyBeagle 12y ago
But if zeroing memory is necessary for the program to be correct, hang the cost. I don't know what sort of "real time applications" would require gambling on the initial state of memory. If you really can't afford to use dynamic memory, don't. 'C' will cheerfully allow you to hog as much as you want outside the heap.
- shadowfox 12y ago
  > But if zeroing memory is necessary for the program to be correct, hang the cost. Sure. And your application should bear that cost and not necessarily every application written in C. Maybe there is a case for using a safer malloc implementation for your program? > I don't know what sort of "real time applications" would require gambling on the initial state of memory. This isn't really gambling. If you know you are going to initialize the memory with sane values immediately (and this is a common practice), it is a waste to do that initial zeroing.
  - ArkyBeagle 12y ago
    Ah - in that case, I'd agree. I couldn't draw to that conclusion from the text provided - that's just as good as zeroing ( and, as you say ) renders the zeroing moot.

3 ms·

Zeroing memory is certainly not free, and if you're doing some types of real-time applications, can have a significant cost. http://randomascii.wordpress.com/2

by Narishma 12y ago

pkolaczk 12y ago
If the compiler could prove you never read an array element before writing (like it is most of the time in Java, and should be all of the time in C), it could optimize the entire zeroing step away. Java does this very often. And initializing your variables close to the point of declaring them is a good practice in C anyways, which should make it easy for the compiler to analyze.
ArkyBeagle 12y ago
But if zeroing memory is necessary for the program to be correct, hang the cost. I don't know what sort of "real time applications" would require gambling on the initial state of memory. If you really can't afford to use dynamic memory, don't. 'C' will cheerfully allow you to hog as much as you want outside the heap.
- shadowfox 12y ago
  > But if zeroing memory is necessary for the program to be correct, hang the cost. Sure. And your application should bear that cost and not necessarily every application written in C. Maybe there is a case for using a safer malloc implementation for your program? > I don't know what sort of "real time applications" would require gambling on the initial state of memory. This isn't really gambling. If you know you are going to initialize the memory with sane values immediately (and this is a common practice), it is a waste to do that initial zeroing.
  - ArkyBeagle 12y ago
    Ah - in that case, I'd agree. I couldn't draw to that conclusion from the text provided - that's just as good as zeroing ( and, as you say ) renders the zeroing moot.