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    SubjectRe: [STATUS 2.5] May 1, 2002
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    Stephen Lord <lord@sgi.com> writes:

    > On Wed, 2002-05-01 at 16:38, Andrew Morton wrote:
    > > Mike Fedyk wrote:
    > > >
    > > > On Wed, May 01, 2002 at 09:53:37AM -0400, Guillaume Boissiere wrote:
    > > > > new framebuffer layer, as well as some more delayed disk block
    > > > > allocation bits.
    > > >
    > > > Actually Andrews work on address_space based writeback is related somewhat,
    > > > but really it's a rewrite/cleanup of the buffer layer. Delayed block
    > > > alocation is helped alot by this, and almost depends on it IIRC.
    > > >
    > > > One vote for a seperate listing in the status for "Address Space based
    > > > Writeback / Buffer layer cleanup".
    > >
    > > Well the next major step here is going direct
    > > pagecache<->BIO, bypassing the intermediate submit_bh
    > > for most I/O.
    > >
    > > Probably that will make most of the performance benefits
    > > of delayed-allocate go away.
    >
    > Most of the performance benefits of delayed allocate are that
    > you do not the hard work of allocating the disk space in each
    > write call, you get to do it once, in potentially larger chunks,
    > and often not in the user's context.

    Except for moving the work out of the users context, ext2 gets
    a similar benefit by reserving disk space ahead of time. So it isn't
    clear that you need to have a delayed allocation to achieve this.

    Eric
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