Forcing performance mode for background app on Intel P/E-core CPU

On Intel 12th and 13th gen. CPUs with P- and E-cores the Windows 11 scheduler heavily prioritizes the E-cores for apps that are not being drawn on the screen (i.e. whose window is minimized or completely covered by another foreground app). This leads to poor performance of demanding multi-threaded background tasks such as video encoding. I don't know if apps can override being shoved onto the E-cores when in the background via some Windows API, but let's say it's an older app that is unaware of that - is there a way to override the scheduler for a specific process and forec it to stay in high-performance mode even if its window is not in the foreground (i.e. not drawn on the screen)?

Setting the priority of the process in the task manager to "high" doesn't change the behavior, and the power plan is already set to "high performance" (min. and max. CPU performance at 100%). It's a regular PC with an Intel 13900K CPU, not a laptop, running Windows 11 with the latest updates as of this day. Is there a way to force performance mode "per-process"?

See if this will work. settings>display<scroll to bottom and select graphics>select a app from the list and change its settings.

glasskuter said:

See if this will work. settings>display<scroll to bottom and select graphics>select a app from the list and change its settings.

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I added the program to the list and set its graphics performance to "high performance" but it didn't make any difference when the app is in the background. I assume it only affects GPU related performance, not the P/E-core assignment.

I've got a i9-13900k in my PC, I don't recall ever seeing anything about changing the performance and efficient cores settings and functionality for apps.

Try setting a higher priority to the running task/ process in taskmanager, don't set it too high though or you could lock up the machine.

DigitalGoat said:

Try setting a higher priority to the running task/ process in taskmanager, don't set it too high though or you could lock up the machine.

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As I said in the first post, increasing the process priority doesn't change the background behavior. There's no competition for resources when the app is in the background, so that's not something the process priority is supposed to change.

Novgorod said:

As I said in the first post, increasing the process priority doesn't change the background behavior. There's no competition for resources when the app is in the background, so that's not something the process priority is supposed to change.

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Apologies, for some reason only the first paragraph of your post was showing when I first read it, an issue on my end I'm sure.
There is a way to disable the E-cores (or a least there was when the P & E architecture released originally), the idea being for game and anti cheat compatability. Although it is not an ideal or long term solution for you it could acheive what you are after, if you just need the performance for the app in question occasionally, as long as loosing a certain core count temporarily would not cause an issue.

DigitalGoat said:

There is a way to disable the E-cores (or a least there was when the P & E architecture released originally)

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I know it's a "workaround" to set the CPU affinity to only the P-cores in the task manager, but for a highly multithreaded task (like video encoding) that would be a significant performance loss overall (especially with a 13900K which has 16 E-cores).

I think this background performance issue doesn't happen if the process uses 100% of all available cores because there's nowhere to shove it. But let's say the process uses only 28 out of the 32 available threads (16P/16E) - if it's in the foreground it gets assigned all 16 P-core threads and 12 E-core threads; in the background the assignment is reversed, i.e. it fills up all 16 E-core threads first and gets only 12 P-core threads. But that's still better performance than 16 P-core threads and 0 E-core threads, so disabling the E-cores would only benefit (e.g.) games with a low thread count. Though if I'm not mistaken, this workaround for games was for Windows 10 which is (or was?) unaware of P/E-cores. Games on Windows 11 should get P-core priority when in the foreground.

Novgorod said:

I know it's a "workaround" to set the CPU affinity to only the P-cores in the task manager, but for a highly multithreaded task (like video encoding) that would be a significant performance loss overall (especially with a 13900K which has 16 E-cores).

I think this background performance issue doesn't happen if the process uses 100% of all available cores because there's nowhere to shove it. But let's say the process uses only 28 out of the 32 available threads (16P/16E) - if it's in the foreground it gets assigned all 16 P-core threads and 12 E-core threads; in the background the assignment is reversed, i.e. it fills up all 16 E-core threads first and gets only 12 P-core threads. But that's still better performance than 16 P-core threads and 0 E-core threads, so disabling the E-cores would only benefit (e.g.) games with a low thread count. Though if I'm not mistaken, this workaround for games was for Windows 10 which is (or was?) unaware of P/E-cores. Games on Windows 11 should get P-core priority when in the foreground.

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Yeah you are right of course, the performance hit may be too much.
I would think that the scheduler is capable of moving background task threads to performance cores if the app spawning the thread useage requires it, then moving them back to E-cores.
I don't see why an app running in the background is always limited to E-cores and refused P-core assignment if required, that just seems a very inefficient use of the CPU's abilities.
Of course that is just my thoughts on the matter.

I believe the E-core disabling was more down to games and anti cheat specifically not coping with E-cores rather than it being a Windows 10 issue inherently, once the games and anti cheat apps were patched/ updated it was no longer required. Of course Win10 also got a scheduler update to help with the new architecture.

DigitalGoat said:

I don't see why an app running in the background is always limited to E-cores and refused P-core assignment if required, that just seems a very inefficient use of the CPU's abilities.

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I don't think it's limited to E-cores, rather it prioritizes E-cores but also uses P-cores if it runs out of available idling E-cores. I guess a low thread count background app would always be stuck with E-cores (if it's the only app running at full blast), unless it can somehow request for P-cores specifically. If that's a thing in the current Windows API then surely there must be a tool to override the scheduler behavior for any app...

Novgorod said:

I don't think it's limited to E-cores, rather it prioritizes E-cores but also uses P-cores if it runs out of available idling E-cores. I guess a low thread count background app would always be stuck with E-cores (if it's the only app running at full blast), unless it can somehow request for P-cores specifically. If that's a thing in the current Windows API then surely there must be a tool to override the scheduler behavior for any app...

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Going on a whim here but have you tried looking at Nirnsoft's tools, they seem to have one for everything, just about... maybe you can find what you want there? Most of the utilities are free or free for personal use.

The optimization between the processor and Windows Task Scheduler relies on Intel® Thread Director technology. Intel's Thread Director is a microcontroller built in each Alder Lake processor (12th Generation Intel Core processors ) that is optimized for Windows 11 Task Scheduler to decide which thread goes where (P-core or E-core).

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So it's not up to Windows or OS settings to control which cores are used.

Here is a guide on how to disable E cores, you should be able to find similar settings in BIOS.

This should prevent use of E cores completely.

DigitalGoat said:

Going on a whim here but have you tried looking at Nirnsoft's tools, they seem to have one for everything, just about...

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The tools are great but unfortunately a bit dated. There's nothing there related to P/E-core issues because that stuff is brand new...
Here is someone having the same issue but apparently he solved it by running his encoder app as administrator. I have UAC disabled, so I'm running everything as administrator and still have the issue.

zebal said:

So it's not up to Windows or OS settings to control which cores are used.

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That's obviously not the case because Intel Thread Director is unaware which app window is in the background, that's up to the OS to decide and then mark the process as "prioritize E-cores". I also don't want to disable the E-cores because that's half of the CPU performance.

Novgorod said:

That's obviously not the case because Intel Thread Director is unaware which app window is in the background

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This would be the case if Intel Thread Director would not be intermediatory between OS and CPU, but that's not the case.
To my understanding ITD receives info from OS, does decision making and forwards it to CPU.

Novgorod said:

I also don't want to disable the E-cores because that's half of the CPU performance.

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I think you can't have it both ways.

zebal said:

To my understanding ITD receives info from OS, does decision making and forwards it to CPU.

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Yes, the Thread Director receives info from the OS scheduler about process priority (performance/power requirements) and assigns P/E-cores accordingly. But it's the OS that's doing the flagging (i.e. requesting performance or "efficiency" mode), so I just want Windows not to flag my process as a "background task" ever, then it will get assigned the P-cores first like any other foreground process.

@Novgorod
In task manager when you right click a process there is an options saying "Efficiency mode"
Does enabling that for process in background work?

edit:
See also:

zebal said:

@Novgorod
In task manager when you right click a process there is an options saying "Efficiency mode"
Does enabling that for process in background work?

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Yes, it gives a warning but I can enable it manually for any process. It seems to do the opposite of what I want to achieve though :)..

@Novgorod
See my edit, there is also a button to disable it per process, see if there is "green leaf" for process in background
Other than this there is no option to control Windows thread scheduler.

If setting high priority of a process doesn't work then IDK.
it's a feature of a CPU not an issue.

@zebal Efficiency mode was never enabled for that particular process, it appears that this mode is not enabled by default unless the app or the user requests for it (for example, some sub-processess of Chrome or Firefox have efficiency mode enabled but almost all other apps don't). The "green leaf" is a power saving function (for laptops or environmentalists) and not active when the power plan is "high performance".

I found a program called "Process Lasso" which seems to support lots of power/performance options. I'll test whether this can solve my problem - though it would be much more convenient to have a built-in function for it, since the API most certainly exists...

You can try installing ...


... And see if there are some vendor specific options

The software interface exposes a set of robust capabilities common in most enthusiast platforms along with new features available on new Intel® application processors and Intel® motherboards.

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