lkml.org 
[lkml]   [2002]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: (fwd) Re: [RFC] mount flag "direct"
    Date
    "Anton Altaparmakov wrote:"
    > At 09:57 06/09/02, Peter T. Breuer wrote:
    > >"Anton Altaparmakov wrote:"
    > >I've had a look now. I concur that e2fs at least is full of assumptions
    > >that it has various different sorts of metadata in memory at all times.
    > >I can't rewrite that, or even add a "warning will robinson" callback to
    > >vfs, as I intended. What I can do, I think, is ..
    >
    > Oh, you saw the light. (-: I can assure you that most file systems make

    The question is if they do it in a way I can read. If I can read it, I
    can fix it. There was too much noise inside e2fs to see a point or points
    of intercept. So the intercept has to be higher, and ..

    > direct_IO, I plan to keep all metadata caching in place, just stop caching
    > the actual file data. That should give maximum performance I think.

    But not correct behaviour wrt metadata in a shared disk fs. And your
    calculation of "maximum performance" is off. Look, you seem to forget
    this:

    suppose that I make the FS twice as slow as before by meddling with
    it to make it sharable

    then I simply share it among 4 nodes to get a two times _speed up_
    overall.

    That's the basic idea. Details left to reader.

    I.e. I don't care if it gets slower. We are talking thousands of nodes
    here. Only the detail of the topology is affected by the real numbers.

    > >.. simply do a dput of the fs root directory from time to time, from
    > >vfs - whenever I think it is appropriate. As far as I can see from my
    > >quick look that may cause the dcache path off that to be GC'ed. And
    > >that may be enough to do a few experiments for O_DIRDIRECT.
    >
    > What does "GC" mean?

    Garbage collection. I assume that either there is a point at which the
    dcache is swept or as I free a dentry from the cache its dependents
    are swept. I don't know which. Feel free to enlighten me. My question
    is simply "is doing a dput of the base directory dentry on the FS
    enough to clear the dcache for that FS"?

    Peter
    -
    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 13:22    [W:3.222 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site