Faster way to zero memory than with memset?

Question

I learned that memset(ptr, 0, nbytes) is really fast, but is there a faster way (at least on x86)?

I assume that memset uses mov, however w

Answer 1

Unless you have specific needs or know that your compiler/stdlib is sucky, stick with memset. It's general-purpose, and should have decent performance in general. Also, compilers might have an easier time optimizing/inlining memset() because it can have intrinsic support for it.

For instance, Visual C++ will often generate inline versions of memcpy/memset that are as small as a call to the library function, thus avoiding push/call/ret overhead. And there's further possible optimizations when the size parameter can be evaluated at compile-time.

That said, if you have specific needs (where size will always be tiny *or* huge), you can gain speed boosts by dropping down to assembly level. For instance, using write-through operations for zeroing huge chunks of memory without polluting your L2 cache.

But it all depends - and for normal stuff, please stick to memset/memcpy :)