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    SubjectRe: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

    >> The patches have gone through a large number of revisions, have been
    >> heavily tested and reviewed by a few people. The memory footprint of this
    >> approach is smaller than introducing new zones. If the cache footprint,
    >> increased branches and instructions were a problem, I would expect
    >> them to
    >> show up in the aim9 benchmark or the benchmark that ran ghostscript
    >> multiple times on a large file.
    > I appreciate that a lot of work has gone into them. You must appreciate
    > that they add a reasonable amount of complexity and a non-zero perormance
    > cost to the page allocator.

    The patches do ad a reasonable amount of complexity to the page allocator. In
    my opinion that is the only downside of these patches, even though it is a big
    one. What we need to decide as a community is if there is a less complex way to
    do this, and if there isn't a less complex way then is the benefit worth the
    increased complexity.

    As to the non-zero performance cost, I think hard numbers should carry more
    weight than they have been given in this area. Mel has posted hard numbers that
    say the patches are a wash with respect to performance. I don't see any
    evidence to contradict those results.

    >> The will need high order allocations if we want to provide HugeTLB pages
    >> to userspace on-demand rather than reserving at boot-time. This is a
    >> future problem, but it's one that is not worth tackling until the
    >> fragmentation problem is fixed first.
    > Sure. In what form, we haven't agreed. I vote zones! :)

    I'd like to hear more details of how zones would be less complex while still
    solving the problem. I just don't get it.
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