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SubjectRe: process creation time increases linearly with shmem
Date

> 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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