On Wed, Oct 24, 2018 at 07:21:19PM -0700, Joel Fernandes wrote:

On Wed, Oct 24, 2018 at 10:37:16AM +0200, Peter Zijlstra wrote:

quoted

On Fri, Oct 12, 2018 at 06:31:57PM -0700, Joel Fernandes (Google) wrote:

quoted

This series speeds up mremap(2) syscall by copying page tables at the
PMD level even for non-THP systems. There is concern that the extra
'address' argument that mremap passes to pte_alloc may do something
subtle architecture related in the future that may make the scheme not
work.  Also we find that there is no point in passing the 'address' to
pte_alloc since its unused. So this patch therefore removes this
argument tree-wide resulting in a nice negative diff as well. Also
ensuring along the way that the enabled architectures do not do anything
funky with 'address' argument that goes unnoticed by the optimization.

Did you happen to look at the history of where that address argument
came from? -- just being curious here. ISTR something vague about
architectures having different paging structure for different memory
ranges.

I didn't happen to do that analysis but from code analysis, no architecutre
is using it. Since its unused in the kernel, may be such architectures don't
exist or were removed, so we don't need to bother? Could you share more about
your concern with the removal of this argument?

No concerns at all with removing it; I was purely curious as to the
origin of the unused argument. Kirill provided that answer.