lkml.org 
[lkml]   [2001]   [Oct]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: 2.4.14-pre6

    On Wed, 31 Oct 2001, Andrew Morton wrote:
    >
    > But it's actually quite seductive to take a huge amount of data and
    > just chuck it at the request layer and let Jens sort it out. This
    > usually works well and keeps the complexity in one place.

    Fair enough, I see your point. How would you suggest we handle the latency
    thing, though?

    I'm not against making the elevator more intelligent, and you have a
    good argument. But I've very much against "allow the queues to grow with
    no sense of latency".

    > One does wonder whether everything is working as it should, though.
    > Creating those 100,000 4k files is going to require writeout of
    > how many blocks? 120,000? And four minutes is enough time for
    > 34,000 seven-millisecond seeks. And ext2 is pretty good at laying
    > things out contiguously. These numbers don't gel.
    >
    > Ah-ha. Look at the sync_inodes stuff:
    >
    > for (zillions of files) {
    > filemap_fdatasync(file)
    > filemap_fdatawait(file)
    > }
    >
    > If we turn this into
    >
    > for (zillions of files)
    > filemap_fdatasync(file)
    > for (zillions of files)
    > filemap_fdatawait(file)

    Good catch, I bet you're right.

    > kupdate runs this code path as well. Why is there any need for
    > kupdate to wait on the writes?

    At least historically (and I think it's still true in some cases),
    kupdated was also in charge of trying to write out buffers under
    low-memory circumstances. And without any throttling, blind writing can
    make things worse.

    However, the request throttle should be _plenty_ good enough, so I think
    you're right.

    Oh, one issue in case you're going to work on this: kupdated does need to
    do the "wait_for_locked_buffers()" at some point, as that is also what
    moves buffers from the locked list to the clean list. But that has nothing
    to do with the fdatawait thing.

    Linus

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:12    [W:11.088 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site