Path: utzoo!attcan!uunet!wuarchive!rex!ames!eos!ptolemy!raymond
From: raymond@ptolemy.arc.nasa.gov (Eric A. Raymond)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: (Disk) Cache problems...
Keywords: Cache
Message-ID: <3071@einstein.ptolemy.arc.nasa.gov>
Date: 26 Nov 89 03:15:40 GMT
References: <638@ariadne.csi.forth.GR>
Reply-To: raymond@einstein.arc.nasa.gov.UUCP (Eric A. Raymond)
Distribution: comp
Organization: NASA Ames Research Center
Lines: 39

In article <638@ariadne.csi.forth.GR> bluguras@csi.forth.gr (Blougouras Dimitris) writes:
>                         No Cache     |  PC-CACHE  
>                        --------------+---------------
>          Norton's DI      1.9        |    4.9    
>          Coretest       202.9 Kb/sec |  985.6 Kb/sec
>          Compiling       77 sec      |   75 sec
>    
>          This means that when I compile a C program I develop, I see NO
>          difference in compile times, whether using the cache or not.

What this probably means is that your cache is too small / your file
input needs for a compile too large.  Caches work when you can save
reading from the disk by reading a version stored in memory.  In your
case, your compiler accesses much more disk space then it can store in
your cache.  Therefore, much of the cached data is flushed by new data
before it can be reused.

The reason the cache show's an improvement on the other tests, is that
a larger portion of the data acessed is in the cache when it is
retrieved.


Solutions:
  - get a bigger cache.  This is probably not that realistic and may
    not give you the results your are looking for (based upon the
    overhead of a cache as it's size grows).

  - use a ramdisk for things that you alwys want fast access to.  This
    requires a bit more thought than a cache and isn't tolerant to
    machine errors if you are going to be writing to these files.
    >> Anyone know of a ramdisk/cache that shadows a directory or set
    of files???  That is, a ramdisk that fills up only with entries
    from a given directory (on the fly), and is write through (changes
    to the file go to disk and ram). <<

Note:  The BUFFERS=xxx in your config.sys is also a cache.
-- 
Eric A. Raymond  (raymond@ptolemy.arc.nasa.gov)
G7 C7 G7 G#7 G7 G+13 C7 GM7 Am7 Bm7 Bd7 Am7 C7 Do13 G7 C7 G7 D+13: Elmore James