Process Lasso Documentation

Process Lasso is Windows process automation and optimization software. From tuning algorithms like ProBalance to user-created rules and persistent settings such as CPU affinities and priority classes, Process Lasso enables you full control over running applications!

Our famous ProBalance algorithm maintains system responsiveness during high CPU loads. This proprietary algorithm dynamically adjusts the priorities of running programs so that some are given higher priority access to the CPU(s) than others. With ProBalance, no longer will single, or multiple, processes be able to bring your system to a virtual stall. Process Lasso will let you keep interacting with your computer, even when it is under a heavy CPU load. Try our CPUEater Demo to experience ProBalance for yourself.

Process Lasso also allows users to automate and tweak how applications are run through a number of unique and helpful functions. These include persistent priority classes, persistent CPU affinities, disallowed processes, per-process power profiles, a process watchdog for advanced rules, process instance count limits, instance or app balancing and much more! These features give you the ability to control how programs utilize your computer’s resources based on automatically applied settings. With Process Lasso, you can decide exactly how you want your processes to run.

Many additional functions such as power plan automation, a system responsiveness metric and process activity logging are also available.

For minimal resource use, all algorithms and process rules are enforced by a stand-alone background service called the Process Governor. The GUI is entirely optional.

OS Compatibility

Workstation edition: Windows 7, 8, 10, 11
Server edition: Windows 2012, 2012R2, 2016, 2019
For Windows XP, 2003, and Vista see this version. For Windows 2000, go back to this version.

[ Docs as PDF (older) ]


  1. Components
  2. Features
  3. About ProBalance
    1. What’s the problem?
    2. How does ProBalance work?
    3. Proof of concept (CPUEater demo)
  4. About Performance Mode (Gaming Mode)
  5. Using the Graphical User Interface (GUI)
    1. The Main Window
    2. Graph
      1. Per-process CPU history
    3. All Processes Tab
      1. Select what process information to show
      2. Rules column meaning
      3. Single selection process context menu
      4. Multiple selection process context menu
    4. Active Processes Tab
      1. Select what process information to show
      2. Double clicking a process
      3. Single selection process context menu
      4. Multiple selection process context menu
    5. Features and Configuration
      1. CPU Limiter
      2. Instance Balancer
      3. Priority Classes
      4. CPU Affinities
      5. CPU Sets
      6. ProBalance Options
      7. Auto-Terminate List
      8. Process Watchdog
      9. Instance Count Limits
      10. Keep Running Processes
      11. SmartTrim
      12. Performance (Gaming) Mode
      13. Anti-sleep processes
      14. Application Power Profiles
      15. Processor Group Extender
      16. Sampling (process logging)
      17. Config Profile Switcher
      18. Global Toggle: Forced Mode
    6. Process Matching using Regular Expressions
    7. Main Menu Options
  6. Using The Core Engine
    1. Overview
    2. Running as a Service
  7. Using the INI Configuration File
  8. System configuration tools
    1. TweakScheduler
    2. Vista Multimedia Scheduler Tool
  9. Deployment on Servers
    1. Methods
    2. Installation
    3. Config and Log Paths
    4. Pushing or Pulling Config and Log
  10. Command Line Arguments
    1. Installer Command Line
    2. GUI Command Line
    3. Governor Command Line
  11. Frequently Asked Questions

Components of Process Lasso

Process Lasso consists of a core engine and a user interface. The two are separated so that users can completely close the user interface while keeping Process Lasso active, managing processes. The core engine is run as ProcessGovernor.exe, while the user interface is ProcessLasso.exe. Running only the core engine results in memory usage of a mere 1-3MB (typically) and almost no CPU use.

When the user interface, ProcessLasso.exe, is launched it automatically launches an instance of the ProcessGovernor.exe core engine if one isn’t already running for the current user, or as a service. When you close the user interface, you are asked whether you want to keep the core engine running or not.

By default, each user session has their own instance of ProcessLasso.exe and ProcessGovernor.exe. An alternate popular configuration would be to run the governor as a service and the GUI as-necessary.

Component Filename Description
Graphical User Interface (GUI) ProcessLasso.exe This graphical user interface (GUI) serves the purposes of configuring process rules and features, displaying running processes and recent activity (logs) by the Process Governor service. It also hosts the system tray icon.
Core Engine (Governor) ProcessGovernor.exe This non-interactive system service, called the Process Governor or ‘core engine’, does the actual work of applying process rules and algorithms. It can run stand-alone without the GUI for minimal resource use.
Session Agent bitsumsessionagent.exe This tiny process facilitates the Governor’s retrieval of select information about each interactive user session, namely the foreground process ID and the last input time (for the idle timer). This is used by ProBalance and IdleSaver. If these features are not in use, this process can be disabled.
Configuration File prolasso.ini This configuration file holds the process rules and options for Process Lasso. The path can be changed via ‘Options / General / Reconfigure Startup…’.
Log File prolasso.log This log file keeps a record of recent actions. It can be disabled. The path can be changed using ‘Options / General / Reconfigure Startup…’. This file is in a CSV format.

Automation and Features

ProBalance is our famously efficacious algorithm to maintain PC responsive during high CPU loads.
CPU Affinities
Set persistent CPU affinities so that processes run on the desired set of CPUs every time they launch.
CPU Sets
A ‘weaker’ from of CPU Affinities, preferred cores.
Priority Classes
Set persistent CPU, I/O, and memory priorities so that processes run at the desired priorities every time they launch.
Disallowed Processes
Immediately terminate any matched process, by your criteria.
Limit Instances
Limit the number of instances a process may have in a user session.
Instance Balancer
Spread CPU cores among running instances of application(s).
CPU Limiter
Dynamically, temporarily limit CPU utilization of a process when it reaches a threshold.
Group Extender
Enable processor group unaware applications to make full use of the CPU.
Keep Running
Automatically restart select processes when they terminate.
Power Profile Automation
Switch power plans while idle (IdleSaver), or when specified process(es) are found running, or by a manual timer (Keep Awake), etc…
Prevent Sleep (Keep Awake)
Process Lasso can prevent your PC from sleeping for a specified amount of time, or when select processes are running.
Disable Hyper-Threading or SMT
Dynamically disable Hyper-Threading or SMT on a per-process basis.
Advanced Watchdog Rules
Create advanced rules to perform a specified action when matched process(es) reach a certain threshold of resource consumption or other criteria.
Multi-select Operations
Perform an operation like terminate on multiple processes at once!
Configuration Profiles
Profiles allows for creation and use of multiple rule configurations.
Process Lasso contains numerous other features and functions. Explore them for yourself!

Main Window

The main window consists of a CPU utilization and system responsiveness graph, a list of running processes, and a list of recent actions (log). The configuration of Process Lasso is made easy to tweak through the menu system. In the main menu you’ll find all the general configuration options. Right-clicking on a process, or multiple processes, shows available operations on those process(es).

Process Lasso main window

Parked CPU cores shown in grey

Parked CPU cores shown in grey

The Graph

The Process Lasso graph shows a calculation of system responsiveness and overall CPU utilization. The system responsiveness is calculated using a proprietary algorithm that measures the latency in the user interface (windowing) subsystem.

Highlighted portions of the graph indicate that a ProBalance process restraint occurred during that period. This can help you see the impact of Process Lasso on system responsiveness. Note that the highlighted areas of the graph may not be 100% accurate in their timing, but are somewhere very close. As future versions come the accuracy of the highlighted area will improve.

Highlighted ProBalance events

During periods when ProBalance takes action to ensure your system responsiveness remains high despite a spike in CPU use, the graph will be highlighted. The log can be referenced to see what actions were taken.

Lasso Graph

Note these colors may now be reversed in recent versions!

Hovering over a highlight event will show you the process(es) adjusted (in priority or CPU affinity) at that time.


CPU history of selected process(es)

With Process Lasso you can see the individual CPU history of process(es) you select in the process list. The CPU utilization history of all processes currently selected (highlighted) in the process list is drawn as a smaller white line on the graph. For example, the user below selected ‘devenv.exe’ and its CPU history was drawn onto the graph as a white line.


The All Processes Tab

The Process List shows running processes and allows for easy rule creation. You can right click on any process, or on multiple processes, to get a context menu of available options. Among many other things, the options include setting current priorities and affinities, as well as default priorities and affinities.

Single process context menu

The context menu when multiple processes are selected is different than when a single process is selected, since not all operations can be performed on multiple processes.

Multi-select process context menu

Process Lasso Terminate Multiple Processes at once

Select Multiple Processes

With Process Lasso you can select multiple processes at once and operate on them. Not all functions are available when multiple processes are selected, but most common ones are.

Selecting which columns to show

You can select which columns you want visible by right-clicking on the ‘All processes’ tab, right-clicking on the list header, or using the ‘View / Select Process Columns’ menu. In addition, you can resize the columns (at their headers) and change the column ordering by dragging the column headers. These view changes will be remembered by Process Lasso. The same applies for the ‘Active processes’ tab. Note that right-clicking the ‘Active processes’ tab allows for setting process information shown in that column. Information in the ‘Active processes’ tab is more limited than information in the ‘All processes’ tab. However, double clicking on any process in the ‘Active processes’ tab will take you to its entry in hte ‘All processes’ tab.

The ‘Rules’ column of the GUI gives a summary of rules that match each process.


Format: [X][L][_][x][W][g][K][#n][d|D][e][p][Mx][t][s][iX][<..<<<<][RHANBI][0-63]

Character(s) Meaning
X Excluded from ProBalance
L CPU Limited
_ Instance Balanced
W A watchdog rule is set
g Process induces Performance Mode
K Keep running (restart if terminates)
#n Instance count limit of n, e.g. #2 for a limit of 2
d|D Prevents sleep of PC, or PC and display, respectively
x Excluded from foreground boosting
e IdleSaver is disabled when this process is running
p Process will cause the PC to enter a particular Power Profile
Mx Where ‘x’ is the persistent memory priority set for this process.
t Excluded from SmartTrim
R Persistent priority class: Real time
H Persistent priority class: Highest
A Persistent priority class: Above normal
N Persistent priority class: Normal
B Persistent priority class: Below normal
I Persistent priority class: Idle
ih Persistent I/O priority class: High
in Persistent I/O priority class: Normal
il Persistent I/O priority class: Low
ib Persistent I/O priority class: Very Low (background)
0-63 Persistent CPU affinity, i.e. ‘0-2,3,5’ for cores 0,1,2,3,5
< Hard Throttle level lowest
<< Hard Throttle level low
<<< Hard Throttle level moderate
<<<< Hard Throttle level high

The Active Processes Tab

Selecting which columns to show

You can select which columns you want visible in the ‘Active Processes’ tab the same way you can in the ‘All Processes’ tab. by right-clicking on the ‘Active processes’ tab or by right-clicking on the list header. In addition, you can resize the columns (at their headers) and change the column ordering by dragging the column headers. These view changes will be remembered by Process Lasso. Double clicking on any process in the ‘Active processes’ tab will take you to its entry in the ‘All processes’ tab, where additional information is available.

Process Lasso Active Processes Tab

Active Processes Tab

The Active Processes tab shows only processes that are actively utilizing the system CPU(s). It displays basic information about them, and a horizontal bar graph to visually depict their active CPU utilization.

Right-clicking on one or more of the processes in the ‘Active Processes’ list show the same context menu as found in the ‘All Processes’ tab.
Double-clicking on a process in the ‘Active Processes’ list will find the corresponding process in the ‘All Processes’ tab and make it visible.

Double clicking a process in the active processes view

You can double click a process in the ‘Active processes’ tab to go to that process in the ‘All processes’ tab, where extended information is available.

Keyboard Shortcuts

Terminate selected processes (forcible)
Select All processes in current view

CPU Limiter

  • Menu path: ‘Options / CPU / CPU Limiter …’

First, it is important to note that the CPU Limiter is not a magic bullet to reduce CPU utilization without consequence. CPU utilization occurs because a process is doing something. Limiting that consumption will slow or otherwise impact the process. Our ProBalance technology does wonders for system responsiveness during high loads without actually reducing CPU use.

However, in some circumstances, it is desirable to reduce a process’s CPU use to achieve more fair access to system resources. This is common in Remote Desktop Services (RDS) environments, or when non-critical background processes are consuming too large a share of system resources. In those cases, the CPU Limiter is a great option.

The CPU Limiter can dynamically reduce the CPU use of running processes by temporarily constraining their CPU affinity. For instance, on a 4 CPU core system, constraining the CPU affinity by 1 core limits the total possible CPU utilization of that process to 75%.

CPU Limiter Log Events

The user creates rules telling the CPU Limiter which processes to act on, and when. When a process match exceeds a threshold over some period, it is limited for the configured duration. Like other rules in Process Lasso, process matches can include wildcards and user names.

The CPU cores removed from a process’s CPU affinity are selected randomly from the set of its original CPU affinity. Once the act-for duration elapses, the original CPU affinity is restored.

While one could accomplish a similar function with a combination of Watchdog rules, the CPU Limiter is easier to use. Using the Watchdog for the same effect would require two rules, one to constrain the CPU affinity when over threshold, and another to restore the original CPU affinity. Finally, the Watchdog rules are limited to statically defined CPU affinities.

The act-for duration can be set to 0 to indicate an indefinite change to a process’s CPU affinity.

Example Use Case

Let’s say you have an issue with Chrome sometimes consuming all available CPU cycles, and you don’t want to set a static CPU affinity that restricts it from short bursts of 100% utilization. You might create a CPU Limiter rule such as:

chrome.exe, after 15 seconds over 30%, restrict by 2 cores for 30 seconds

If a specific user is problematic, you can append that user name to the process match:


Wildcards are also supported in process and user names, such as:


If no user is specified, then any user matches.

This feature supports Regular Expressions for more complex and precise matching.

Demo video of the CPU Limiter

Instance Balancer

  • Menu path: ‘Options / CPU / Instance Balancer …’

The Instance Balancer spreads the CPU across running process instances, of either the same or multiple applications (when using advanced match rules). When there are more instances than allotted CPU cores, instances are ‘stacked’ in a round-robin manner. When the instance count of managed applications changes by new process creation or termination, a re-balance occurs.

All children of a process can be matched with a ‘childof: ‘ prefix, such as childof: boinc.exe. Alternatively, it can be accomplished with RegEx, e.g. /^([^,]*,){5}boinc\.exe.*,/.

Equal CPUs per instance
Distributes CPU cores evenly across matching process instances, dynamically adjusting as new instances run or terminate.
Specific core count per instance
Assigns a fixed number of CPU cores to each matching process instance.

This feature supports Regular Expressions for more complex and precise matching.

Demo video of the Instance Balancer

Priority Classes

  • Menu path: ‘Options / CPU / CPU Priorities …’

Persistent CPU Priority Classes are available to keep applications running at specific priorities.

Note that use of above-normal priority classes is generally ineffectual at improving performance (it won’t make an app go faster). Instead, it is recommended to target problematic background processes with Below Normal and Idle priority classes to limit their impact on performance sensitive applications. This is what ProBalance does automatically.

Priority classes available in Windows are:

  • Real-Time
  • High
  • Above Normal
  • Normal
  • Below Normal
  • Idle

CPU Affinities

  • Menu path: ‘Options / CPU / CPU Affinities …’

CPU Affinities control which CPU cores a process is allowed to use. Its threads will only be scheduled to that set of CPUs. This is useful to limit max CPU consumption of a process, or to optimize which CPU cores are dedicated to specific apps, games or services.

If you want to instead dynamically reduce the set of CPU cores a process has access to, try the CPU Limiter.

User should also sett the CPU Sets feature, a softer form of CPU affinities that also support multiple processor groups.

Multi-group (>64 logical CPU cores) processes have system restrictions on CPU affinities. Process Lasso will make a best effort to move threads to your chosen CPU affinity, but new threads of a process won’t be constrained to the desired CPU affinity without continuous reapplication of the affinity. Process Lasso will do this automatically if you create a persistent CPU affinity rule. However, you may instead want to use the CPU Sets feature, a weaker form of CPU affinity, since it does not have these multi-group restrictions.


CPU Sets

  • Menu path: ‘Options / CPU / CPU Sets…’

CPU Sets are a ‘weaker’ form of CPU Affinities. Instead of a hard contract, they are a suggestion of preferred CPU cores. The OS will try to abide by a CPU Set, but has discretion to schedule outside the Set. This may be necessary when the thread load exceeds the number of cores in the Set, or for power management reasons. CPU Sets may often be the better choice than traditional ‘strong’ CPU Affinities.

On Intel 12th Gen CPUs (Alder Lake), CPU Sets can be used to signal the OS to only utilize Performance (P) or Efficient (E) cores, or some mix of each, for a process. Many users will find CPU Sets an ideal method to disable E-cores for select applications.

For systems with more than 64 logical CPU cores, CPU Sets are also processor group aware, and a process’s CPU Sets may span multiple processor groups.

Persistent (Sticky) CPU Sets are fully supported by Process Lasso.

Read more about CPU Sets at MSDN.

CPU Sets Rules Dialog

CPU Sets Rules Dialog

CPU Sets Selection Dialog

CPU Sets Selection Dialog


ProBalance Options

  • Menu path: ‘Options / CPU / ProBalance’

There are several advanced ProBalance parameters that can be adjusted, but generally the defaults are good and the user should be cautious tweaking these settings.

ProBalance Advanced Configuration Dialog

ProBalance advanced options let you control if and when ProBalance should act.

ProBalance Exclusions

It is often not necessary to set name based ProBalance exclusions since the other factors taken into consideration cause ProBalance to ignore most processes that shouldn’t be acted on. However, if you notice a process being acted on by ProBalance in the logs or Insights that you don’t want touched, then you can specify a named exclusion.

This feature supports Regular Expressions for more complex and precise matching.

Auto-Terminate List

  • Menu path: ‘Options / Control / Disallowed Processes …’

The processes listed here will get terminated when they are found to be running. Process Lasso can not (at present) actually prevent them from trying to start up, it just immediately terminates them when it finds them running.


Process Watchdog

  • Menu path: ‘Options / Control / Watchdog (advanced rules) …’

The process watchdog (advanced rules) allows for you to take an action on a process when it exceeds a certain amount of CPU or Memory. You can specify actions such as Restart, Terminate, Log, Execute (external), or Change Affinity. With both memory and CPU triggers, you can set a time the process must exceed this threshold before action is taken..

There are several actions and trigger types.


  • CPU
  • Memory


  • Change CPU Affinity
  • Execute
  • Log Occurrence
  • Restart Process
  • Set CPU Priority Class
  • Set I/O Priority Class
  • Stop Processing Rules
  • Terminate Process
  • Trim Virtual Memory


  • Divide CPU % thresholds by system CPU count
    Divide CPU thresholds by the total logical core count. For example, 3200% could be given, and when divided by 64 cores, would be a threshold of 50% of total CPU use. This allows for more precision on high core count systems.

This feature supports Regular Expressions for more complex and precise matching.

Instance Count Limits

  • Menu path: ‘Options / Control/ Instance Count Limits …’

The user can limit the number of instances of a process allowed to be running at the same time (per user session) with this dialog. New instances of processes will be terminated if they match a pattern here and the number of instances is already equal to, or greater than, the instance count limit.

Keep Running Processes

  • Menu path: ‘Options / Control / Keep Running (auto-restart) …’

The user can ensure certain processes are kept running by entering in this dialog. This way, they can restart on crash, or restart if they become unresponsive. You can set this by right-clicking on a process, using the ‘Keep process running’, or by using application menu option at ‘Options / Configure Keep running processes …’.

NOTE: Processes are always launched unelevated. You can change this behavior by creating a registry value in HKEY_LOCAL_MACHINE\Software\ProcessLasso named “AllowElevatedChildren” with a DWORD type and value of 1 (get .REG file here). By default, this registry key can only be written by elevated administrators. This will still not allow a process to be launched with rights in excess of the governor. Therefore, if the governor is running in a limited user context, any child process will inherit only that context. When the governor is running as a service, launches are prohibited, and the Keep Running function is disabled.


  • Menu path: ‘Options / Power/ IdleSaver …’

IdleSaver allows the user to set a power plan for use when the system is Idle. This allows the user to run in a high performance power plan while active, but without completely sacrifice energy savings by switching to a more conservative power plan when the user is idle.


  • Menu path: ‘Options / Memory/ SmartTrim Options …’

SmartTrim is an intelligent memory management algorithm that can trim working sets on a per-process basis when thresholds are reached, and can also clear the system standby list (cache).

Performance Mode

  • Menu path: ‘Options / Power / Performance Mode’

The user can designate certain processes to ‘Induce Performance Mode’. This causes Process Lasso to enter a specific power profile, Bitsum Highest Performance by default, when those applications are run. In this way, it is similar to the ‘Application Power Profiles’ feature. However, Performance Mode also makes certain adjustments to ProBalance in an effort to ensure  the performance-critical application runs without interference from background processes. Users designate a ‘High Performance’ process by right-clicking on a process and checking the ‘Induce Performance Mode’ menu item, or by using application menu option at ‘Options / Power / Performance Mode / Designate High Performance processes …’.


Induce Performance Mode process context menu item

Induce Performance Mode process context menu item

Users can select an alternate power plan to use with Performance Mode, instead of the default of Bitsum Highest Performance.

Select alternate power plan for Performance Mode

Select alternate power plan for Performance Mode

Anti-sleep Processes

  • Menu path: ‘Options / Power / Keep Awake …’

The user can prevent the PC and display from entering a sleep or hibernate state by adding them to the ‘anti-sleep’ list. This can be done by right-clicking on a process, using the ‘When running’ menu, or by using application menu option at ‘Options / Configure Anti-Sleep processes …’.

Application Power Profiles

  • Menu path: ‘Options / Power / Application Power Profiles …’

The user can create rules to that cause the system to enter the chosen power profile when specified processes are running. When they terminate, the system is returned to the previous power profile. This lets users target their system power profile for currently running applications. You can do this by right-clicking on a process, using the ‘Application power profile‘ submenu, or by the menu option at ‘Options / Power / Application Power Profiles ….

Processor Group Extender

Process Lasso 9.7 adds the Processor Group Extender. This novel algorithm allows processor group unaware applications to make use of the full CPU. It accomplishes this by monitoring threads of target processes and dynamically assigning threads to supplemental processor groups as required.

Processor groups are only used on systems with more than 64 logical cores. Since Windows CPU affinities are represented as 64-bit bitmasks, processor groups were introduced to extend support to more than 64 logical cores. Thus, a CPU affinity applies to only a single processor group, and each process is assigned a default processor group when it launches. A process’s threads are restricted to that default group unless they are manually assigned to other processor groups. Typically, this thread assignment is done by the application itself. Applications that are able to assign their threads to other processor groups are group aware.

Group unaware applications will therefore be limited to a single processor group, leaving CPU cores in the other group(s) underutilized. Ideally, the application developer would update their software to be group aware, but for cases where that hasn’t happened, Bitsum now has a solution! We call it the Processor Group Extender. It monitors threads of target processes and assigns excess threads to supplemental processor groups.

Note that the Processor Group Extender is only necessary, and should only be used, in situations where an application needs additional CPU cores, but is not processor group aware. Unnecessary or inappropriate use may affect the performance characteristics of an application.

Processor Group Extender

Processor Group Extender

Config Profile Switcher

Config Profiles, found at submenu ‘File / Config Profile‘, are named collections of all process rules and settings. This allows users to create sets of rules for specific workloads, for instance ‘Gaming’ and ‘Productivity’. Previously, these config profiles had limited utility because they couldn’t be automatically switched to when a particular process was run.

The Config Profile Switcher fills the gap by switching config profiles when specified processes are run. When a matched process later terminates, the prior config profile will be restored. Each config profile should have rules to undo any changes made by other profiles, e.g. setting a CPU affinity back to all cores.

This feature should be used sparingly. If multiple simultaneous running processes match different config switcher rules, only the oldest process will have its config enforced.

The Config Profile Switcher supports wildcards and advanced process match rules.

Config Profile Switcher

Config Profile Switcher

Forced Mode

Forced Mode, available in the Options menu, is a toggle that causes rules to be continuously re-applied to running processes. This can be desirable in the case of a process that changes its own settings. Normally, Process Lasso would make a one-time adjustment to each new instance of a process, but Forced Mode causes it to evaluate whether the target settings (e.g. CPU affinity or priority class) were changed, and re-apply them if so.

Sampling (process logging)

Process sampling capabilities can periodically dump a snapshot of process performance data to a CSV. Users can reach this feature through ‘Options / Log settings / Configure sampling’. This is distinct from the primary Process Lasso log, shows events such as process creation, termination, rule and algorithm enforcement.

The output is appended to a CSV file. Date and time placeholders allow for generation of unique CSV files for given periods. No rotation or pruning of emitted CSV files is performed, so they will grow indefinitely while sampling is enabled.

Format specifiers:

%yyyy% = 4 digit year
%mm% = month
%dd% = day
%hh% = hour
%mm% = minute
%ss% = second

Periodic snapshots of performance data (sampling)


Process Lasso works wonders on Windows Servers, including Remote Desktop Services (Terminal Services). It can prevent a single user or process from monopolizing the server’s CPU resources, improve responsiveness, and allow for full control of running processes.

The fact that the core engine (governor) is separate from the GUI makes it easy to install without it being visible to the end user.

For Servers, the distinct Server Edition of Process Lasso, with a 30-day free trial available. See this page for more information.


Process Lasso’s installer can run from the CLI without interaction. This is done by adding the /S switch to the installer command line.

The INI configuration file may need to be precomposed with the desired rules. For that, we recommend installing Process Lasso on a workstation and using the GUI to create the rules.

The installation command might look like:

ProcessLassoSetup64.exe /S /gui_start_type=manual /governor_start_type=service /keyfile=prolasso.key /importconfigfrom=\\somepath\lasso\prolasso.ini

Key files for easier product activation or offline use can be requested by contacting Bitsum. They are available on to Site and Server Edition licensees.

For a full listing of installer command line options, see this page.

Alternatively, Process Lasso’s binaries could be directly embedded in your software packages. In that case, after deployment, you’d launch processgovernor.exe with the command line switch /ConfigFolder=xxx. Launching the GUI (processlasso.exe) may not be necessary, depending on your use case. Please contact us if you require guidance on manual configuration.

Governor Startup Type

Towards the end of the install process, a set of two dialogs exposes settings relevant to how Process Lasso and its core engine (Governor) should start. In the first dialog, the administrator can choose whether the GUI should start for all users, the current admin user, or not auto-start. The GUI does not need to be running for rules to be enforced by the ‘Governor’, aka ‘the core engine’.  The Governor is entirely non-interactive, runs in the background, and has no visible presence. The GUI hosts the system tray icon and main Process Lasso window.

For the Governor, there are two primary choices:

  1. Service – Governor runs as a service (GaaS),  managing all processes on the system (recommended and default option)
  2. Normal process – Governor runs as a normal process hosted in an administrative session, managing all processes on the system.

Config and Log Paths

In the config and log path presented in the second dialog, users can choose to use a centralized network configuration and log store, a per-machine store, or a per-user store.

Option 1: Centralized config and log

In this mode, all workstation are configured to either (1) use a centralized configuration and log path hosted on a network share OR (2) use a machine local configuration and/or log path, but have a centralized INI configuration file pushed out to clients when changed, and the logs pulled from clients periodically.

If the INI config path is a network share, it is polled for changes at least once a minute. For local paths, file-system change events are used to get notification of changes, so no polling is required and changes will be picked up instantaneously.

Option 2: Per-workstation configuration file and log

In this mode, you’d install Process Lasso on each workstation and use a common configuration and log path that every user of the system would access.

Option 3: Some combination of the above, or an alternate method

In the end, you can utilize Process Lasso just about however you want. You could have workstations launch it from a network share, for instance, without ever having to install Process Lasso on those workstations.

Pushing or Pulling Config and Log

When pushing Process Lasso configuration changes out to local machine storage, it is recommended to use a script or other automated means to copy the Process Lasso configuration file to the target machines. As soon as the configuration file is over-written, Process Lasso will adopt it (no app restart necessary). Alternatively, the configuration file can be pulled by end devices.

Similarly, the log files can be periodically pulled from devices.

More help?

If you have any questions about getting Process Lasso up and running in your enterprise, please contact us. Customized solutions are also available.

Command Line Arguments

Installer Command Line

Switch (defaults in bold) Description Examples
/S (case sensitive) Performs a silent installation, also known as non-interactive or unattended. Since no configuration dialogs will be shown during install, you should compliment this switch with others (listed below) to specify how you would like Process Lasso configured. ProcessLassoSetup.exe /S

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  • Slovenian (1060)
  • Japanese (1041)
  • Dutch (1043)
  • TradChinese (1028)
  • SimpChinese (2052)
  • ..(others)..
This indicates the language to use. If this value is not supplied, it defaults to English. Do not try to use unsupported languages, and be sure your language name is spelled as listed here (i.e. SimpChinese). Alternatively, you can specify the language’s code page number. ProcessLassoSetup.exe /S /language=English ProcessLassoSetup.exe /S /language=1033 
ProcessLassoSetup.exe /S /language=German ProcessLassoSetup.exe /S /language=1031 
ProcessLassoSetup.exe /S /language=Slovenian 
ProcessLassoSetup.exe /S /language=Italian 
ProcessLassoSetup.exe /S /language=SimpChinese
/gui_start_type=[all|current|manual][,uac] This indicates whether to start the GUI at login for ALL users (all), for only the current user (current), or neither (manual). The current user is the user context in which the installer is running. Add ‘UAC’ anywhere to this parameter to indicate that it should launch the governor with elevated permissions in Vista, Windows 7, Windows Server 2008, and above. ProcessLassoSetup.exe /S /gui_start_type=all 
ProcessLassoSetup.exe /S /gui_start_type=current 
ProcessLassoSetup.exe /S /gui_start_type=manual 
ProcessLassoSetup.exe /S /gui_start_type=all,UAC
/governor_start_type=[all|current|service|manual][,uac] This indicates whether to start the core engine (processgovernor) at login for ALL users (all), for only the current user (current), as a service, or neither (manual). The current user is the user context in which the installer is running. When /governor_start_type=service, the /username and /password switches can be used as modifiers to indicate in what user context the service should run. If a username and password isn’t supplied, it will run in the system context. Add ‘UAC’ anywhere to this parameter to indicate that it should launch the governor with elevated permissions in Vista, Windows 7, Windows Server 2008, and above. ProcessLassoSetup.exe /S /governor_start_type=all 
ProcessLassoSetup.exe /S /governor_start_type=current 
ProcessLassoSetup.exe /S /governor_start_type=service 
ProcessLassoSetup.exe /S /governor_start_type=service /username=myuser /password=mypass 
ProcessLassoSetup.exe /S /governor_start_type=all,UAC /username=myuser /password=mypass
/logfolder=[folder] This indicates to use a global log folder for ALL users on the system. By default, each user has his or her own log folder in their respective application data directory. However, it is sometimes desirable to consolidate all log events into a single log folder. Be sure that this log folder is writable by contexts the governor will be running in. If set to run as a normal process, this may mean all users. If set to run as a service, it should be writable by the service user (or SYSTEM user). ProcessLassoSetup.exe /S /logfolder=c:\systemlogs 
ProcessLassoSetup.exe /S /logfolder=c:\systemlogs
/configfolder=[folder] This indicates to use a global configuration folder for ALL users on the system. By default, each user has his or her own configuration in their respective application data directory. However,it is sometimes desirable to use the same configuration for all users, and is required when the governor is run as a service. Be sure that this configuration folder is readable by all user contexts the governor will be running in, and writable by those who you wish to allow configuration changes. ProcessLassoSetup.exe /S /configfolder=c:\pl_config 
ProcessLassoSetup.exe /S /configfolder=c:\pl_config
/launch_gui=[true|false] This indicates whether or not to launch the GUI after installation. Even when the GUI is launched, it remains minimized to the system tray. ProcessLassoSetup.exe /S /launch_gui=true
/importconfigfrom=[path] This indicates to import the configuration from the file you’ve specified. This should be used in conjunction with /configfolder. The file you specify here will be the initial configuration for Process Lasso. You can specify only a folder OR a specific filename here. If you specify only a folder, “prolasso.ini” will simply be appended to the path name. ProcessLassoSetup.exe /S /configfolder=c:\pl_config /importconfigfrom=c:\temp 
ProcessLassoSetup.exe /S /configfolder=c:\pl_config /importconfigfrom=c:\temp\my_default_config.ini
When running the core engine as a service (/governor_start_type=service), these switches can be used to indicate under which user you should start the service. The user MUST have permission to ‘logon as a service’ (see our FAQ for info on allowing that). If a specific user is not supplied, the core engine will run in the system context. Please remember that the Windows user password is case sensitive. ProcessLassoSetup.exe /S /governor_start_type=service /username=myuser /password=mypass
/configpw=[password] This sets the configuration password. This password is required for by the GUI when a user tries to make a change to the configuration file. Use this parameter without a value to remove any existing password. ProcessLassoSetup.exe /S /configpw=somepassword
/key=[licensekey] This sets the license key. ProcessLassoSetup.exe /S /key=1A79A4D60DE6718E8E5B326E338AE533
/keyfile=[keyfile] This is the absolute path of the key file. Do not use a relative path. ProcessLassoSetup.exe /S /keyfile=c:\users\admin\downloads\prolasso.key


ProcessLasso.exe Command Line Parameters

Command line arguments for the GUI and core engine are available. You can use them to over-ride the configuration and log paths, but this is not normally necessary or recommended. Changes to the configuration and log paths should instead be performed by the installer (preferred) or the InstallHelper application.

Switch Description Examples
/Tray Causes the main window to not be immediately displayed. ProcessLasso.exe /tray
/ConfigFolder= Indicates the configuration folder that should be used. It is assumed that ‘prolasso.ini’ will exist in it. If not, it one be created with default values. ProcessLasso.exe /ConfigFolder=”c:\program files\Process Lasso\config”
ProcessLasso.exe /ConfigFolder=c:\config\
ProcessLasso.exe /ConfigFolder=\\server1\ProcessLassoConfig\
/LogFolder= Indicates the folder containing the log files. This folder requires read and write access. ProcessLasso.exe /LogFolder=\\server1\logfolder
ProcessLasso.exe /LogFolder=c:\pslogs
/Config Invokes the ProBalance configuration dialog. This is primarily only used by the installer. Note that this creates a separate instance of Process Lasso that displays the configuration dialog, then exits when the dialog is closed. ProcessLasso.exe /config
/no_raise_existing Start a new instance of ProcessLasso.exe only if it is not already running, but do not show the window of existing instance as would be the default behavior. ProcessLasso.exe /no_raise_existing
/SetActiveProfile=name Switch to active configuration profile to the indicated preexisting named profile. This command does not launch Process Lasso, it exits after changing the profile. ProcessLasso.exe /SetActiveProfile=myprofile
/StartWithProfile=name Switch to configuration profile, then launch Process Lasso. ProcessLasso.exe /StartWithProfile=myprofile

ProcessGovernor.exe Command Line Parameters

Switch Description Examples
/ConfigFolder= Indicates the configuration folder that should be used. It is assumed that ‘prolasso.ini’ will exist in it. If not, it one be created with default values. ProcessGovernor.exe /ConfigFolder=”c:\program files\Process Lasso\”
ProcessGovernor.exe /ConfigFolder=c:\config\
ProcessGovernor.exe /ConfigFolder=\\server1\ProcessLassoConfig\
/LogFolder= Indicates the folder containing the log files. This folder requires read and write access. ProcessGovernor.exe /LogFolder=\\server1\logfolder
ProcessGovernor.exe /LogFolder=c:\pslogs


Process Matching

When matching rules to processes, a match phrase is given by the user, often called the ‘process match’ in Process Lasso. This can be a simple process name, a string with wildcards, or even a Regular Expression checked against multiple process attributes (e.g. user and command line).


Traditional process name matching uses a simple wildcard match, with ‘?’ indicating any single character and ‘*’ indicating a sequence of any character. It is case insensitive. The user name may be appended to the match string with a colon. Depending on the feature, after toggling on path or command line matching, those fields are also compared to the match phrase.

Examples (non-Regex):

 Match any process named chrome.exe

 Match any process that begins with 'chrome'

 Match any process named chrome.exe running under user 'bob'

 Match any process whose parent is boinc.exe (primarily for Instance Balancer)

Regular Expressions

Process Lasso supports Regular Expression (RegEx) matching to multiple process attributes. This allows for the creation of complex rules that were not previously possible. For instance, a rule could act on Chrome.exe or Firefox.exe when user is Bob or Jeremy. Previously, this would require 4 different rules, and in the case of the Instance Balancer, combining them into a single group was not possible.

Features supporting RegEx:

  • CPU Limiter
  • Instance Balancer
  • Watchdog
  • ProBalance Exclusions
  • Persistent CPU Affinities (as of 9.5.7 beta)

Support for RegEx will be come to other features in future versions of Process Lasso.

What is a Regular Expression?

A Regular Expression is a language for pattern matching (and substitution). It has been in use for decades and enjoys widespread support.

A regular expression is a special text string for describing a search pattern. You can think of regular expressions as wildcards on steroids. You are probably familiar with wildcard notations such as *.txt to find all text files in a file manager. The regex equivalent is .*\.txt.

Read more:
Quick Reference (Microsoft)
RegEx101 Tester

Use of RegEx in Process Lasso

When matching a RegEx, Process Lasso concatenates multiple fields about the process. The format of this consolidated process information string is:

PID,User,Process,Path,ParentPID,Parent,,,,CommandLine (always last)
process ID
user under which process is running
basename of process
file path of process image
parent ID
parent process name
instance command line (this field is always last. Its index is subject to change if new fields are inserted later!)

In this way, an expression can match to anything in the concatenated string, or only to specific fields, depending on how precise the expression is.

With Process Lasso, Regular Expressions are differentiated from traditional match phrases by encapsulation in forward slashes (e.g. ‘/myregex/’).

All matching is case insensitive. Embedded commas in a field (normally only in the command line field) are escaped with a backslash, so for precise rules this should be taken into account.


While RegEx allows for powerful matching on multiple patterns and fields, it can also be used in simple ways:

 Match 'firefox?exe' anywhere in any field. Note '.' is a wildcard in RegEx, but you can escape it like 'firefox\.exe' for more precision.

 Match only 'firefox.exe' at the start of a field (>0)

 Match only 'fire*exe' at the start of a field (>0)

 Match 'fire*exe' or 'chr*exe' at the start of a field (>0)

 Match if any field is app1.exe, app2.exe, or app3.exe (>0)

 Match user 'bobsmith' at the start of a field (>0)

 Match '-type=renderer' anywhere in last field (command line). Note starts with a comma, then ends before a new field occurs (see below for embedded commas).

 Prior with handling of escaped embedded commas in the command line.

To match specific fields, an expression such as this can be used to match specifically field 3 (the process name):

 ^ = Starts at beginning of string
 ([^,]*,) = Not a comma repeated zero or more times, followed by a comma
 {2} = Repeat prior match (a comma delimited field) 2 times
 Match processes with username of jeremy or bob

 Match processes named chrome.exe

 Match processes whose name contains with ‘chr’

 Match processes ‘chrome.exe’ or 'firefox.exe'

 Match processes whose parent is ‘boinc.exe’

 Match processes whose name is chrome.exe under user of jeremy or bob.

 Match process name ‘chrome.exe’ and has '-type=renderer' in the command line (last field)

/^([^,]*,){3}.*\\program files.*/
 Match path containing ‘\Program Files\’ (matching is case insensitive).

How to test Regular Expressions

To test your Regular Expressions, we recommend this site. We’ve preloaded a sample of what you’d be matching against, again with fields being (also see above):

PID,User,Process,Path,ParentPID,Parent,,,,CommandLine (always last)

Alternatively, create a text file with row(s) simulating Process Lasso’s provided match string. Then use grep (WSL or Linux) or another tool to match RegEx. Note that the encapsulating forward slashes need to be removed. An example is:

20116,jeremy,chrome.exe,C:\Program Files (x86)\Google\Chrome\Application\chrome.exe,19233,chrome.exe,,,,"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --type=renderer
test command:
grep -P 'chr.*' sample.txt