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    SubjectRe: [PATCH 0/5] Reducing fragmentation using zones
    Mel Gorman wrote:
    > To satisfy this request, I did a quick rebase of the list-based approach
    > against 2.6.16-rc1-mm1 to have a comparable set of benchmarks. I will post
    > the patches in the morning after a re-read.
    Thank you.

    > So, in terms of performance on this set of tests, both approachs perform
    > roughly the same as the stock kernel in terms of absolute performance. In
    > terms of high-order allocations, zone-based appears to do better under
    > load. However, if you look at the zones that are used, you will see that
    > zone-based appears to do as well as list-based *only* because it has the
    > EASYRCLM zone to play with. list-based was way better at keeping the
    > normal zone defragmented as well as highmem which is especially obvious
    > when tested at rest. list-based was able to allocate 83 huge pages from
    > ZONE_NORMAL at rest while zone-based only managed 8.
    yes, this is intersiting point :)
    list-based one can defrag NORMAL zone.
    The point will be "does we need to defrag NORMAL ?" , I think.
    IMHO, I don't like to use NORMAL zone to alloc higher-order pages...

    > Secondly, zone-based requires careful configuration to be successful. If
    > booted with kernelcore=896MB for example, it only performs slightly better
    > than the standard kernel. If booted with kernelcore=1024MB, it tends to
    > perform slightly worse (more zone fallbacks I guess) and still only
    > manages slighly better satisfaction of high order pages.
    This is because HIGHMEM is too small, right ?

    > On the flip side, zone-based code changes are easier to understand than
    > the list-based ones (at least in terms of volume of code changes). The
    > zone-based gives guarantees on what will happen in the future while
    > list-based is best-effort.
    > In terms of fragmentation, I still think that list-based is better overall
    > without configuration.
    I agree here.

    >The results above also represent the best possible
    > configuration with zone-based versus no configuration at all against
    > list-based. In an environment with changing workloads a constant reality,
    > I bet that list-based would win overall.
    On x86, NORMAL is only 896M anyway. there is no discussion.

    Honestly, I don't have enough experience with machines which doesn't have Highmem.
    How large kernelcore should be ?
    It looks using list-based and zone-based at the same time will make all people happy...

    -- Kame

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      Last update: 2006-01-20 02:20    [W:0.026 / U:2.028 seconds]
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