[lkml]   [2002]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [BK][PATCH] Reiser4, will double Linux FS performance, pleaseapply
    On Nov 04, 2002  23:30 -0800, reiser wrote:
    > The appropriate setting of
    > transaction max age depends on the user. The setting we chose is
    > appropriate for software developers doing compiles. It is not clear to
    > me yet what the right setting is. Perhaps 3 minutes is more
    > appropriate. I was probably overly influenced by Drew Roselli's
    > statistics on how long the cyle is between rewrites. Her statistics are
    > probably skewed by having lots of CS students using the machines she got
    > her data from. 5 seconds is too short to perform good layout
    > optimization for subsequent reads.

    I think the bdflush defaults are (were?) something like 5 seconds for
    metadata, and 30 seconds for file data. reiser4 should (if it doesn't
    already) use the parameters set by sys_bdflush() to tune the writeout

    I would think that either:
    a) A file was completely written in under 30 seconds (e.g. untar or gcc
    or whatever else you are doing), so deferring allocation and writing
    to disk does not help you at all.
    b) A file is continuing to be written for more than 30 seconds that
    has a very large amount of outstanding data which can be committed
    to disk with (probably) the same read optimization quality as any
    larger amount of data.
    c) A file is continuing to be written for more than 30 seconds that
    is growing slowly and no matter how long you defer the write you
    will only get an incremental read layout. Presumably you could do
    something to pre-allocate/reserve a bunch of space at the end of this
    file as it continues to grow.

    So, except for the very unusual case of files with lifespans between 30
    seconds and 300 seconds, or files that are written to between those
    intervals, I would guess that you are not gaining much extra benefit by
    deferring the writes another 270 seconds.

    Cheers, Andreas
    Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
    \ would they cancel out, leaving him still hungry?" -- Dogbert
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:30    [W:0.022 / U:29.024 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site