Manual:$wgSVGMaxSize

Details
The smaller side of a SVG will never be scaled to greater than this.

For example, if this setting is left unchanged at 2048 pixels, an attempt to rasterize a 200×100 SVG to 4000×2000 will succeed (since 2000 ≤ 2048). However, an attempt to rasterize it to 5000×2500 will generate a 4096×2048 image instead.