Sizing JVMs and VM Memory

How to estimate the amount of JVM heap and host memory requirement in complex cases where there are more JVM instances per VM and more apps per JVM and have different usage requirement per app ?

let's see some of the metrics to collect to construct an equation on estimating the sizes.

• list the apps per instance. Ideally there will be multiple apps deployed on one instance of JVM and all these apps are not equally used and each app will have its own characteristics thus have uneven memory requirements i.e. based on req. classes, code logic and constructs etc.,

• And identify the 'typical' transactions.. ideally, in any app, 20% of features are executed 80% of times

• Take a first measurement - server start up heap. Once the server is up completely, get the first point after a full GC (hotspot) or first OC (jrockit)

• Now, ideally the first user access is demanding one as it loads lot of stuff. So, do just logins into each of the app and take a note of OCs/FGCs for each user. So, per app, the numbers gives the amount of heap required for first login

• So, XMS - to make it good enough, it can be sum of (server startup heap + sum of all above deltas )

• Now, exercise the typical 20% transaction as single user per app and do not logout - so these are typical active users on the system - call these deltas as h1, h2 etc . This can be on a warmed up server but best is to have no other logged in users in the system. Each delta can be noted or take the final delta after all different app users are in and executed the typical flows but not logged out.

• XMX i.e. the max amount of memory can be XMS + ( total delta * (%app1 conc. users)   +  ... )

for hotspot jvms or other jvms where there are more heap spaces like young/survivor, perm etc., they can be calculated as proportionate ratio of XMX ..

And, typical host memory usage requirement can be calculated as approx 1.8 times of XMX

If someone can simulate load and want to bare the cost, time and complexity of all setup to do that then it is probably best to get the numbers based on test results.., the benefits in doing so can be not just limited to JVM heap but gives the other resource pools across the layers..

Mobiles - The way they transformed made things reachable to some but created complexity to others

I am talking about the quality checks for the applications built for mobile devices. Mobile devices transformation has to be considered as the fastest change in technology so as the complexity in delivering applications on this new platform which is becoming a must !

Besides making sure the features work i.e. testing the functionality, it is the most important task to ensure the app actually perform as expected. someone can say what is there to think about as it is a light weight code .. there is infact a lot that could disrupt the performance - examples - have to support different vendors like android/APPLE, version of operating systems, underlying hardware, resolutions, GPU, CPUs, memory, network carriers and subscribed bandwidths like 2G/3G/4G, inter-apps interruptions, backend thread support for async calls .. what not !

Well there is a lot, I can think of how one can approach to validate performance of the mobile applications and the upstream servers by using some of the great tools in the market.

Below are some of the tasks to evaluate performance and what these tools can do..

• Test and monitor the app's performance on different emulators. If it has to be done independently then each IDE is needed like android studio, IOS IDE and respective skill set as well. Perfecto addresses this with its support to multiple devices 

• Test the app's performance on different real devices- can't do it manually.. can not have a farm of devices.. perfecto can do it using its mobile device cloud.. or its emulator is good enough as well

• Simulate apps performance under different network speeds on devices/emulators - can do by using various softwares like act but again perfecto along with shunra integration can manage devices by emulating various network bandwidths

• Capture the traffic and simulate 1000's of devices load to app servers - this can be done using emulators and tcp capture.. but perfecto-shunra can do and the captured traffic can be fed to Loadrunner. And, Shunra can virtualize networks to emulate load from different locations/carriers/bandwidths during load tests

• At the same time one would have to recheck the app's performance on the device while server under load  - again by perfecto

Its a different world now with mobiles/tablets/wearables that move .. Apps need to support all these !

Gone are those days where apps are accessed from a standalone PC ..