If you zero upfront, you have to do all of that save the page fault anyway, but for large allocations you also thrash the cache zeroing stuff that's immediately

If you zero upfront, you have to do all of that save the page fault anyway, but for large allocations you also thrash the cache zeroing stuff that's immediately evicted to memory. It really is faster in general to zero a page when the program actually touches it, since that's when the program wants it in cache (for certain thresholds of "large allocation")