NPAG AGGRESSIVE

NPAG_AGGRESSIVE is a system parameter that controls reclamation of nonpaged pool lookaside lists.

Beginning with OpenVMS Version 8.2, the default values of NPAG_ AGGRESSIVE and NPAG_GENTLE are 100. A value of 100 turns off both gentle and aggressive reclamation of nonpaged pool lookaside lists. In many cases, when pool reclamation moves small packets from the lookaside lists back to the variable list, the result is fragmentation of the variable list. This fragmentation appears as many small packets at the front of the variable list and a few large packets at the end of the list. When an allocation occurs for a packet that is larger than any of the lookaside lists, the system must find a large enough packet on the variable list. When heavily fragmented, the entire variable list often must be searched to find a large enough packet. Because the variable list is kept in address order, when a large packet is deallocated, the entire list must be searched again to deallocate the packet.

Under these conditions, system performance can be severely degraded. For this reason, VSI recommends that you turn off pool reclamation but keep both NPAG_AGGRESSIVE and NPAG_GENTLE system parameters set to 100. NPAG_AGGRESSIVE is a DYNAMIC parameter.