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    SubjectRe: pdflush eating a lot of CPU on heavy NFS I/O
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    On Wed, 2004-04-28 at 23:55, Brent Cook wrote:

    > ozma:/home /home nfs rw,v3,rsize=8192,wsize=8192,hard,udp,lock,addr=ozma 0 0

    OK, then it's not the case that it is doing synchronous I/O.

    I see that we're failing to set wbc->encountered_congestion in the case
    where a nonblocking writeback is forced to exit due to congestion. Could
    that be causing pdflush to loop Andrew?

    If so, does the following patch help?

    --- linux-2.6.6-rc3/fs/nfs/write.c.orig 2004-04-28 22:25:46.000000000 -0400
    +++ linux-2.6.6-rc3/fs/nfs/write.c 2004-04-29 00:06:25.000000000 -0400
    @@ -347,8 +347,10 @@ int nfs_writepages(struct address_space
    if (err)
    return err;
    while (test_and_set_bit(BDI_write_congested, &bdi->state) != 0) {
    - if (wbc->nonblocking)
    + if (wbc->nonblocking) {
    + wbc->encountered_congestion = 1;
    return 0;
    + }
    nfs_wait_on_write_congestion(mapping, 0);
    }
    err = nfs_flush_inode(inode, 0, 0, wb_priority(wbc));
    -
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