Re: process creation time increases linearly with shmem

[Andi Kleen]

> Would it be worth trying to do something like this?

Maybe. Shouldn't be very hard though - you just need to check if the VMA is 
backed by an object and if yes don't call copy_page_range for it.

I think it just needs (untested) 

Index: linux-2.6.13-rc5-misc/kernel/fork.c
===================================================================
--- linux-2.6.13-rc5-misc.orig/kernel/fork.c
+++ linux-2.6.13-rc5-misc/kernel/fork.c
@@ -265,7 +265,8 @@ static inline int dup_mmap(struct mm_str
 		rb_parent = &tmp->vm_rb;
 
 		mm->map_count++;
-		retval = copy_page_range(mm, current->mm, tmp);
+		if (!file && !is_vm_hugetlb_page(vma))
+			retval = copy_page_range(mm, current->mm, tmp);
 		spin_unlock(&mm->page_table_lock);
 
 		if (tmp->vm_ops && tmp->vm_ops->open)

But I'm not sure it's a good idea in all cases. Would need a lot of 
benchmarking  at least.

-Andi
-
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