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    SubjectRe: patch: reiserfs for 2.3.49
    Hi!

    > It has long been an architectural weakness of ReiserFS that we allocate block
    > numbers to buffers as we need each buffer. We knew that we should cure this by
    > doing either pre-allocation of blocknrs as ext2 does (meaning allocate many
    > blocks at a time, and then keep them reserved for that file until file close),
    > or allocating block numbers on dirty buffer/page flush as XFS does. It is for
    > sure the case that our current practice of allocating blocks as we need new
    > buffers to write into is a bad architecture. Yura wrote some pre-allocation code
    > that improved our performance by as much as 4x in some benchmarks, but I
    > discouraged it because I prefer allocate on flush. This decision is hurting us
    > at the moment. Pre-allocation is much easier to code (and already written by
    > Yura for an older version), allocate on flush is the right answer long-term.
    > Zam has been working on allocate on flush for about 6 weeks, but it is not ready
    > yet. I think we will have Yura throw in his pre-allocation code

    Does on-disk layout differ between no-prealloc, prealloc, and
    alloc-on-flush versions? Probably not. Then there's no problem getting
    no-prealloc into kernel first ASAP, then changing it to
    alloc-on-flush.
    Pavel

    --
    I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
    Panos Katsaloulis describing me w.r.t. patents me at discuss@linmodems.org

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