> but Linux's cache is coherent Linux achieves that coherency by making O_DIRECT invalidate the page in the page cache. I think it paints a more accurate pictu

> but Linux's cache is coherent Linux achieves that coherency by making O_DIRECT invalidate the page in the page cache. I think it paints a more accurate picture to say the caching is disabled with O_DIRECT, not that it is coherent (although it certainly is).