RE: [PATCH 1/1] Implement shared page tables

[Chen, Kenneth W]

Dave McCracken wrote on Tuesday, August 30, 2005 3:13 PM
> This patch implements page table sharing for all shared memory regions that
> span an entire page table page.  It supports sharing at multiple page
> levels, depending on the architecture.

In function pt_share_pte():

> +		while ((svma = next_shareable_vma(vma, svma, &iter))) {
> +			spgd = pgd_offset(svma->vm_mm, address);
> +			if (pgd_none(*spgd))
> +				continue;
> +
> +			spud = pud_offset(spgd, address);
> +			if (pud_none(*spud))
> +				continue;
> +
> +			spmd = pmd_offset(spud, address);
> +			if (pmd_none(*spmd))
> +				continue;
....
> +			page = pmd_page(*spmd);
> +			pt_increment_share(page);
> +			pmd_populate(vma->vm_mm, pmd, page);
> +		}


Do you really have to iterate through all the vma?  Can't you just break
out of the while loop on first successful match and populating the pmd?
I would think you will find them to be the same pte page. Or did I miss
some thing?


--- ./mm/ptshare.c.orig	2005-09-01 21:16:35.311915518 -0700
+++ ./mm/ptshare.c	2005-09-01 21:18:24.629296992 -0700
@@ -200,6 +200,7 @@ pt_share_pte(struct vm_area_struct *vma,
 			page = pmd_page(*spmd);
 			pt_increment_share(page);
 			pmd_populate(vma->vm_mm, pmd, page);
+			break;
 		}
 	}
 	pte = pte_alloc_map(vma->vm_mm, pmd, address);

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