faster alternative to memcpy?

Question

I have a function that is doing memcpy, but it\'s taking up an enormous amount of cycles. Is there a faster alternative/approach than using memcpy to move a piece of memory?

Answer 1

memory to memory is usually supported in CPU's command set, and memcpy will usually use that. And this is usually the fastest way.

You should check what exactly your CPU is doing. On Linux, watch for swapi in and out and virtual memory effectiveness with sar -B 1 or vmstat 1 or by looking in /proc/memstat. You may see that your copy has to push out a lot of pages to free space, or read them in, etc.

That would mean your problem isn't in what you use for the copy, but how your system uses memory. You may need to decrease file cache or start writing out earlier, or lock the pages in memory, etc.