[Info-vax] Raxco VMS Tuning Seminar Notes

[Bob Koehler]

In article <2bae0454-f09a-45d1-808a-a8fd7e3ffb51 at t13g2000yqm.googlegroups.com>, Neil Rieck <n.rieck at sympatico.ca> writes:
> On Nov 1, 12:10=A0pm, jls <notva... at yahoo.com> wrote:
> 
>>
>> Again with the "always". =A0The drawbacks with this memory management
>> technique are:
>> =A0 =A0 =A0 =A0 1. it uses CPU to constantly manage memory, thus taking
>> available CPU from users =A0This is a trade-off that is not adequately
>> understood by many people.
>> =A0 =A0 =A0 =A0 2. it only takes memory from ACTIVE users, not idle users=
> .
>> This forces the active users to pagefault much more to get work done.
>>
> 
> How could the SWAPPER not trim idle users? They would be faulting at a
> rate of less than PFRATL (if not zero). As I under stand this, you
> would want to trim the working set to a smaller size then swap out
> that smaller set. Not all trimmed pages would ever be faulted back in
> (based upon the theory that you run 10% of the code 90% of the time)

   When PFRATL was non-0, it trimmed idle processes on my systems.  Only
   running processes got page faults at any non-0 rate, and tended to
   grow rather than shrink, because of PFRATH.  By just a little
   gentle tuning I got some RAM starved VAXstations running fine for
   interactive users, with the background processes for DECnet et. al.
   just a swap-in away on the rare occaision when we needed them.