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    SubjectRe: pre-2.3.7-1 fails compile

    Andrea, we've already fixed most pagecache issues. You can find the
    swapping fixes in pre-2.3.7-2-dangerous, and some other fixes are in the
    pipeline as well. (most notably named mappings and there were some bugs in
    buffer.c) As you probably know, this all is work in progress, so please be
    a bit patient before complaining. Swapping (and everything else) is now
    stable here.

    On Mon, 14 Jun 1999, Andrea Arcangeli wrote:

    > Then flushpage may start all the I/O before going to sleep, it may be far
    > more smart simply starting I/O for _all_ dirty buffers and then going to
    > wait for I/O completation. [...]

    this makes a difference only if blocksize != PAGE_SIZE. We have mainly
    concentrated on making the 4k blocksize stuff go like smoke - 1k can and
    will be speeded up later on, but it will probably never perform as well as
    4k ext2fs.

    some read() scalability numbers on a 4-CPU box, using 4k ext2fs:

    1 process reading a 60k file:
    READ: 270.75 MB/sec

    2 processes reading the same 60k file:
    READ: 258.19 MB/sec
    READ: 258.12 MB/sec

    3 processes reading the same 60k file:
    READ: 256.52 MB/sec
    READ: 256.54 MB/sec
    READ: 256.57 MB/sec

    4 processes reading the same 60k file:
    READ: 252.95 MB/sec
    READ: 252.93 MB/sec
    READ: 252.76 MB/sec
    READ: 252.87 MB/sec

    we scale almost perfectly.

    as a comparison, the very same read() workload done on the very same
    user-space buffer, simulated via memcpy:

    MEMCPY: 277.73 MB/sec
    MEMCPY: 277.68 MB/sec
    MEMCPY: 277.72 MB/sec
    MEMCPY: 277.65 MB/sec

    this shows that we are quite close to the physical limit already. And this
    is only the beginning ;)

    -- mingo

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