From: SMTP%"RELAY-INFO-VAX@CRVAX.SRI.COM" 13-APR-1994 13:37:16.56 To: EVERHART CC: Subj: Re: Question about I/O Express From: vtrm01!flaforest@uu7.psi.com (Fred LaForest) X-Newsgroups: comp.os.vms Subject: Re: Question about I/O Express Message-Id: <1994Apr12.095456.122@vtrm01.uucp> Date: 12 Apr 94 09:54:56 EST Organization: Vickers, Inc. - Troy, MI USA Lines: 42 To: Info-VAX@CRVAX.SRI.COM X-Gateway-Source-Info: USENET In article , /I=D/G=DAVID/S=SNEDDON/OU=COMPUTERANDNETWORKOPS/O=WOODSIDEOFFSHOREPETROLEUM/@w writes: > We run I/O Express (V2.2) on our clusters (VMS V5.5-2) and I have noticed > while examining a DECps tabular report of the system performance that up to > 78% of physical memory is counted as being non-paged. ....... I/O Express will make temporary use of free memory when memory demand by other applications is low. As the system work load increase, along with memory needs, I/O Express will release the free pages it has used for cache space back to the free page pool. This works quite well, however, on our system, memory demand was heavy enough at times to keep I/O Express from using any memory for cache space. You can override the automatic space release by telling I/O Express to hold onto a specific number of pages regardless of the load. The cache pages, while in use, are placed in non-paged pool. This is why you had to greatly increase the size of NPAGEVIR (upper limit of non-page space) at installation time. (GOTCHA!) Because it is treated as non-paged space, even if temporarily, VMS will remember how large non-paged space became. The AUTOGEN SAVPARAMS phase will save this HIGH size and use it during the next AUTOGEN to increase NPAGEDYN. I/O Express uses space above NPAGEDYN, guaranteeing that AUTOGEN will see an increased need for larger NPAGEDYN during the next AUTOGEN feedback loop. Each feedback loop will bump NPAGEDYN up and up ... I had one 6310 with 64 Meg of memory with 75% permanently reserved for VMS! I resolved this by using the MAX_NPAGEDYN parameter in MODPARAMS.DAT. This places a cap on the false NPAGEDYN growth. Look at your current "free" non-paged pool size, subtract 200,000, and then subtract that number from your CURRENT NPAGEDYN. This should give you a starting value for your MAX_NPAGEDYN parameter. Get the "free" size during your HEAVIEST system load time. I always try to have at least 200,000 bytes of non-paged space free. Your mileage may vary. -- Fred LaForest UUCP: vtrm01!flaforest VMS/UNIX/(Whatever else we have in the building)/Apple IIgs System Programmer TRINOVA, Inc. GEnie: FALAFOREST Maumee, OH 43537