pagedaemon problem

[Katherine Minister]

Hello again.  We're having a very technical problem with large programs
causing a pagedaemon to thrash.  The system is a 4/260 running SunOS
4.0.1.

The problem we have been experiencing seems to occur when a single
process's virtual address space grows larger than physical memory.  At
this point the pagedaemon runs and reclaims most of the virtual space,
then immediately needs it again and brings it back in.  Thrashing occurs
and CPU utilization drops to between 5-15% (with no other running
processes).  Both the 'vmstat' and 'ps -v' commands indicate many page
faults, although with 32M of physical memory I suppose much time could be
wasted just in fetching pages from the freelist.  Additionally, it seems
as though the resident sent of the text space is being continually
reduced.  Thus a fairly small program with a large data space gets its
resident text space reduced to near nothing (as low as 16 pages as the
process gets old) and it appears that the paging might be mainly in the
text segment.

We think that we can modify the pagedaemon by using adb on vmunix, but
we're not sure exactly what needs to be modified or how.  We think that
several variables need to be changed, in particular 'min_free' ,
'des_free', and perhaps another.  

Any information or experiences in this regard would be most appreciated.

Thanks in advance :-).

	-- Katherine Minister Hosch:  kam at titan.tsd.arlut.utexas.edu