From e798c6e87b64d9fdbd5e9f757b1c033223763d9f Mon Sep 17 00:00:00 2001 From: Prasanna Meda Date: Tue, 21 Jun 2005 17:14:36 -0700 Subject: [PATCH] [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: Prasanna Meda Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/madvise.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 944b5e52d812..75b81ad1f98c 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -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) -- GitLab