>>> On 10/30/2012 at 11:33 AM, Roger Evans <[email protected]> wrote: > Yeah - we'll probably start small, with say half a GB cache and see if > it affects other packages. We use VDISk for paging, and perfmon shows > that we have XSTOR, but no usage.
If z/VM isn't using expanded storage, then the system is not experiencing _any_ pressure on real memory. That's good and bad. The bad part is that you're not using the memory that you paid for to its fullest extent. The good part is that you can add more workload to the system without having to buy more. > I wonder if it would help to put nginx, Memcache and Redis code into a > single VM shared segment. Would it require that the libraries they use > have to be there, too, for that to have any effect? We run nginx on > several linux VM's, so the idea is that it would be used enough that it > wouldn't often be a candidate for paging. If you're thinking of using that DCSS for xip2fs, then no, having the shared libraries in the DCSS is not required. It might provide even more benefit in terms of performance, however, so don't rule it out entirely. In general, memory used by a DCSS is not looked at to be swapped out by CP, if it can help it, so access rates aren't as important as for "normal" pages. One thing we discovered in testing WAS in such a DCSS was that only those pages that actually get referenced get pulled into real storage, so having a large DCSS isn't _necessarily_ going to tie up a lot of real storage. You could also consider having the data in an xip2fs DCSS. If multiple systems are going after read-only access to it, that would certainly cut down on the amount of real memory needed to support multiple instances running on the same box. The downside of course is that generating the DCSS in the first place is not a real high performer, so if the data needs to be recreated every day, that probably wouldn't be something you'd want to do. Mark Post ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
