[lkml]   [2012]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH -mm 2/2] mm: do not reset mm->free_area_cache on every single munmap
    On Thu, Feb 23, 2012 at 01:56:14PM -0800, Andrew Morton wrote:
    > We've been playing whack-a-mole with this search for many years. What
    > about developing a proper data structure with which to locate a
    > suitable-sized hole in O(log(N)) time?

    I intended to implement it a couple of years ago.

    It takes a change to the rbtree code so that when rb_erase and
    rb_insert_color are called, proper methods are called to notify the
    caller that there's been a rotation (probably calling a new
    rb_insert_color_with_metadata(&method(left_rot, right_rot)) ). So that
    these methods can update the new status of the tree. So you can keep
    the "max" hole information for the left and right side of the tree at
    the top node, and if the left side of the tree from the top doesn't
    have a big enough max hole you take the right immediately (if if fits)
    skipping over everything that isn't interesting and you keep doing so
    until the max hole on right or left fits the size of the allocation
    request (and then you find what you were searching for in vma and
    vma->vm_next). It's very tricky but it should be possible. Still it
    would remain generic code in rbtree.c, not actually knowing it's the
    max hole info we're collecting at the root node for left and right
    nodes. Maybe only the left side of the tree max hole needs to be
    collected, not having the right size only means a worst case O(log(N))
    walk on the tree (taking ->right all the time 'till the leaf) so it'd
    be perfectly ok and it may simplify things a lot having only the max
    hole on the left.

    I'm too busy optimizing AutoNUMA even further to delve into this but I
    hope somebody implements it. I thought about exactly this when I've
    seen these patches floating around, so I'm glad you mentioned it.

     \ /
      Last update: 2012-03-20 20:03    [W:0.019 / U:31.816 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site