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Commit e798c6e8 authored by Prasanna Meda's avatar Prasanna Meda Committed by Linus Torvalds
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[PATCH] madvise: do not split the maps 



This attempts to avoid splittings when it is not needed, that is when
vm_flags are same as new flags.  The idea is from the <2.6.11 mlock_fixup
and others.  This will provide base for the next madvise merging patch.

Signed-off-by: default avatarPrasanna Meda <pmeda@akamai.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b15e0905

mm/madvise.c

+16 −11
Original line number Diff line number Diff line
@@ -19,6 +19,21 @@ static long madvise_behavior(struct vm_area_struct * vma, unsigned long start, 
{

	struct mm_struct * mm = vma->vm_mm;

	int error = 0;

	int new_flags = vma->vm_flags & ~VM_READHINTMASK;



	switch (behavior) {

	case MADV_SEQUENTIAL:

		new_flags |= VM_SEQ_READ;

		break;

	case MADV_RANDOM:

		new_flags |= VM_RAND_READ;

		break;

	default:

		break;

	}



	if (new_flags == vma->vm_flags)

		goto out;



	if (start != vma->vm_start) {

		error = split_vma(mm, vma, start, 1);
@@ -36,17 +51,7 @@ static long madvise_behavior(struct vm_area_struct * vma, unsigned long start, 
	 * vm_flags is protected by the mmap_sem held in write mode.

	 */

	VM_ClearReadHint(vma);



	switch (behavior) {

	case MADV_SEQUENTIAL:

		vma->vm_flags |= VM_SEQ_READ;

		break;

	case MADV_RANDOM:

		vma->vm_flags |= VM_RAND_READ;

		break;

	default:

		break;

	}

	vma->vm_flags = new_flags;



out:

	if (error == -ENOMEM)