For my game I need to generate a mesh dynamically. now I'm wondering does it have a noticeable affect in fps if I allocate more vertices than what I'm actually using or not? and does it matter if I'm using DirectX or OpenGL?

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final output will be a w*h cell grid, but for technical issues it's much more easier for me to allocate (w+1)*(h+1) vertices. sure I'll only use w*h vertices in indexing, and I know there is some memory wasting there, but I want to know if it also affect fps or not? (note that mesh is only generated once in each time you play the game)