LoadRunner’s Vugen Run Time Setting Miscellaneous->Multithreading-> Run Vusers as Thread or Process

Though by default Vugen Run Time setting (RTS) is set to run vuser as thread, however, I have seen sometimes testers are struggling to understand why they should use the default setting and why not go for run vuser as process? To sort this confusion out, I thought of writing this article with detailed reasoning behind it.

It’s strongly recommended to set this RTS as 'run vuser as thread'. Reason behind this is explained below in the table which demonstrate the difference between these two settings:

RUN VUSER AS THREAD	RUN VUSER AS PROCESS
When you run Vuser as a thread, LoadRunner (LR) will launch 1 thread per vuser.  e.g. if you will run 50 vusers, LR will launch only 1 process (mdrv.exe) with 50 threads running within that single process (if the limits is set to 50, it can be less or more based on what you customize it from the default value which is 50).	When you run Vuser as process, LR will launch 1 process (mdrv.exe) per vuser. e.g. if you will run 50 vusers, LR will launch 50 mdrv.exe processes.
Running vuser as thread will be more effective on keeping the OS resources consumption on the injector’s boxes to considerably low as this setting does not have very heavy footprints.	Running vuser as process will be very heavy on OS resources consumption on the injector boxes
As multiple threads running within a single process share the available resources among themselves , it’s recommended to use this setting when huge number of vusers are required to run on the injector boxes	As each vuser has its own process and privately allocated resources, it’s not recommended to use this setting when huge number of vusers are required to run on the injector boxes

 

Important points to be considered:

• You will need to check with your development team if application is thread safe or not. If it’s not thread safe, then you may have to choose run vuser as process because running vuser as thread will not work with your application.
• By default, LoadRunner configurations have 50 as the max limit on the number of threads which can run within single process. Though you can increase this number, however, it’s good to keep in mind that by increasing this limit to some unreasonable number will make system/injectors unstable. So, it’s strongly recommended to keep it as default unless HP recommends you to do so.