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    SubjectRe: Linux 2.6.29
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    On Friday 03 April 2009 13:16:08 Linus Torvalds wrote:
    >
    > On Thu, 2 Apr 2009, Jeff Garzik wrote:
    > >
    > > The most interesting thing I found: the SSD does 80 MB/s for the first ~1 GB
    > > or so, then slows down dramatically. After ~2GB, it is down to 32 MB/s.
    > > After ~4GB, it reaches a steady speed around 23 MB/s.
    >
    > Are you sure that isn't an effect of double and triple indirect blocks
    > etc? The metadata updates get more complex for the deeper indirect blocks.
    >
    > Or just our page cache lookup? Maybe our radix tree thing hits something
    > stupid. Although it sure shouldn't be _that_ noticeable.

    Hmm, I don't know what you have in mind. page cache lookup should be
    several orders of magnitude faster than a disk can write the pages out?

    Dirty/writeout/clean cycle still has to lock the radix tree to change
    tags, but that's really not going to be significantly contended (nor
    does it synchronise with simple lookups).


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