I am using nsv arrays to hold session data across multiple page accesses, and to hold some relatively static widely-shared database data to avoid unnecessary database reads. Probably at any point in time there will be several hundred plus nsv arrays with a few K bytes in each, but I haven't spent time to build a good model, and that may be a low estimate. I'm running under RedHat Linux 7.2 with 512MB RAM, OpenACS and PostgreSQL. My site will deliver interactive training, involving light to modest traffic with an average of ten or fifteen database reads / writes per page delivered. I want to be sure the system delivers rapid response time to our users.
Without having read the nsv code, but guessing how it's probably implemented, I am making some assumptions about performance characteristics. Am I far off base? - Since Linux provides a virtual memory facility, there is no practical issue of running out of memory and crashing as long as I apply some restraint in using nsvs. - But of course, if the system has to do a lot of page swapping, performance will degrade. - If I want to purge stale or unaccessed data in the nsv arrays, I have to do it myself. I have read how to set the nsvbuckets parameter and monitor lock contention with mutex monitoring, and can experiment with that. Is there any way to monitor the amount of space consumed by nsv arrays at any point in time? What should I do to monitor the performance impact of my nsv use (other than the mutex monitoring), and perhaps to trigger more aggressive purges - or rewrites :( - when needed? I realize that nscache provides similar facilities. There is so much else on my plate, and my facility with Linux internals is so limited, I hesitate to go down the path of installing it. Would it provide a major improvement, so that I should invest that time and energy? Thanks! Dave
