Tuning SYSVR3 (Esix Rev D) (LONG!)

[Andy Glew]

    One annoying thing I've found about having 2 MB of cache is that the
    system will periodically get incredibly sluggish for a few seconds.

    This happens right after big compiles and links.  I assume it is because
    "sync" is flushing all the dirty buffers.

    Anyone have any idea how to reduce these sluggish periods without reducing
    the cache size and without reducing the reliability of the file system
    with respect to power outages or the performance?

Paradoxically, you can increase the synch scan rate, so that synch is
performed more often.  If you are mainly a read-only environment this
will result in less "jerkiness". 
    Or, you can go the other way, and scan less often.
    I think that the parameter is called BDFLUSHR.

Btw, I have *measured* these effects...  you might be able to lay your
hands on a tuning guide I wrote for a past employer.


Motorola MCD improved on the buffer cache scanning algorithm by
segmenting it, so that it scanned little chunks more frequently.  This
produced a dramatically less jerky interactive response. Once again,
measured.

--
Andy Glew, a-glew at uiuc.edu [get ph nameserver from uxc.cso.uiuc.edu:net/qi]