[PATCH 1/4] treewide: remove unused address argument from pte_alloc functions (v2)

Kirill A. Shutemov kirill at shutemov.name
Thu Oct 25 03:47:03 PDT 2018


On Wed, Oct 24, 2018 at 10:37:16AM +0200, Peter Zijlstra wrote:
> On Fri, Oct 12, 2018 at 06:31:57PM -0700, Joel Fernandes (Google) wrote:
> > 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 see some archicetures (i.e. sparc and, I believe power) used the address
for coloring. It's not needed anymore. Page allocator and SL?B are good
enough now.

See 3c936465249f ("[SPARC64]: Kill pgtable quicklists and use SLAB.")

-- 
 Kirill A. Shutemov



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