Process Lasso is a Windows utility from Bitsum that automates how running processes use the CPU, memory, power plans and other system resources. Real-time algorithms react to load as it happens, while user-defined rules apply priorities, CPU affinities and other settings each time a matching program starts. It runs on Windows desktop and Windows Server systems and comes in a free edition and a paid Pro edition.
Engine and interface
Process Lasso is split into two parts. The Process Governor is a background engine that applies all rules and algorithms. It can run as a system service. The graphical interface serves only to configure them and show what is happening. You can close it while management continues.
The main window combines a graph of CPU use and system responsiveness, a list of running processes and a log of recent actions. Right-clicking one or several processes opens a context menu where you set most rules. A Rules column shows each process’s active settings in shorthand.
ProBalance under heavy load
ProBalance is the algorithm Process Lasso is best known for, and it is on by default. When a background process takes more than a set share of the CPU for a set length of time, ProBalance temporarily lowers its priority class, typically to Below Normal. This changes scheduling order rather than cutting the process off: it still gets plenty of CPU time, and runs at full speed when nothing else is competing. Once the condition passes, the original priority comes back.
ProBalance leaves the foreground application and processes that are not misbehaving alone. While a process is restrained, the tray icon turns red. Name-based exclusions are available, and restrained processes can optionally be put into Efficiency Mode too.
Persistent priorities and core assignment
Settings that Windows normally forgets when a program closes can be made permanent with “Always” rules. Process Lasso handles CPU priority classes from Idle to Real-Time. It also handles I/O priority (a hint about the relative importance of disk access), memory priority (which pages Windows trims first) and GPU priority. Priority rules can also be written to the registry so they apply the moment a process is created.
For core placement there are two approaches:
- CPU affinities are a hard restriction: the process runs only on the selected cores.
- CPU Sets are a preference that the Windows scheduler can step outside of when needed. They suit games and other affinity-sensitive software. On hybrid Intel processors, they can steer a program to performance cores, efficiency cores or both.
Other per-process rules cover Windows 11 Efficiency Mode, disabling SMT for one program and a brief priority boost after launch. Rules can match processes by wildcard, regular expression or parent process, so a rule such as childof:steam.exe covers everything a launcher starts.
Limiting and balancing CPU use
The CPU Limiter caps a program that stays above a CPU threshold for a given period. It removes a chosen number of cores from the process’s affinity for a set time. On a four-core system, taking one core away therefore holds the process to 75% of total CPU. It restores the original affinity afterwards.
The Instance Balancer spreads cores across several running copies of an application. It can divide them equally, give each instance a fixed number of cores or place each instance on its own NUMA node. It rebalances when an instance starts or exits. The Processor Group Extender lets software that does not understand Windows processor groups use all cores on machines with more than 64 logical CPUs.
Watchdog and process control
Watchdog rules work as “if, then” conditions. When a process exceeds a CPU or memory threshold, optionally for a minimum time, Process Lasso can change its affinity or CPU and I/O priority. It can also trim its memory, restart or terminate it, run another program or log the event. Related controls stop disallowed programs as soon as they launch and cap the number of instances of a process per session. They also restart marked programs that crash or stop responding. SmartTrim trims process working sets or clears the standby list when memory thresholds are reached.
Power plan automation
You can start Performance Mode manually for chosen processes or through optional game detection. It switches to the Bitsum Highest Performance plan or another selected plan while those programs run. Application power profiles assign any plan to specific programs and return to the previous one when they exit. IdleSaver uses a faster plan while the user is active and a more economical one when the PC is idle. Keep Awake prevents sleep for a period or while selected processes are running.
Features locked after the Process Lasso trial
Process Lasso Free can be downloaded at no cost and shows a startup reminder. Several advanced features work only during a short trial. After it ends, you cannot add new rules for them: the CPU Limiter, Instance Balancer, Processor Group Extender, application power profiles, sleep prevention tied to programs, Watchdog rules, disallowed processes, instance limits and timer resolution at boot. Saved memory priority rules and Keep Running require Pro, which also adds automatic updates. Commercial use requires a license.
