Multithreading seems to be broken on the BCM28155 chipset(1.2 dual core cortex-a9 and videcore IV HW graphics)

[mckimiaklopa]

MY Device
Android 4.2.2
Samsung Galaxy S Duos 2 S7582
Bcm28155 chip
1.2 ghz dual core cortex-A9
768 mb Ram
Video core 4 Gpu

Turning multithreading on or off does not make any performance impact
On tekken dr for instance,my device produces no difference when this option is on whereas on other devices I tested(dual core mt6577,quad core cortex-a7 snapdragon and intel petium dual core),multithreading produces major speed boost(+10fps increase up to twice fps increase)

All other apps do not havr problems utilizing the second core of my cpu

[mckimiaklopa]

Additional notes about the said issue.

1.Even though the cpu clock is set to default,instead of a stable 30 or 60 internal fps,there are fluctuations happening in the Internal FPS(IN teken Dr for example,the chracter select screen fluctates to 40 internal fps for about 2 seconds before going back to the normal internal fps)
Happens wheter multithreading is on or not and happens to most of my games.
The above does not happen on other devices.

2.Whatever the setting is,the performance on multithreading Off is still the same as multithreading on assuming that the same settings are applied

[mckimiaklopa]

My system Info

The Internal FPS fluctuation i was talking about(cpu clock at default,timer hack is off,happens regardless of MT being on or off)

THE ACTUAL PROBLEM

MT ON,AUTO frameskip 2 Buffered rendering

MT off,auto frameskip 2 Buffered rendering

turning frameskip off or using non-buffered will still make MT on and MT off the same speed

[unknownbrackets]

Its not that it doesn't work, but rather that it doesn't help.

On my device (galaxy s3) it helps only when power saving is off. It still doesn't help a ton and that's just reality. Multi core doesn't help gpu speed (already using shaders) which is often the most limiting factor. Frameskip makes your device draw less, and then there is an opportunity for multithreading to help.

As far as frames per second, we have existing bugs for that.

-[Unknown]

[mckimiaklopa]

Could you reopen the issue?
And could you please investigate or provide some sort of proof or something.

As far as I know ,tekken Dr is a cpu-intensive games.
I know multi-core does not help gpu-intensive games.
But for most of my games' performance,which as far as I know is limited by the CPU and not the GPU,multithreading does not even increase the framerate by at least a single fps which very much puzzles me a lot.
(correct me if i'm wrong but frameskip helps only when the game's performance is limited by the gpu.Thing is frameskip does not make make the framerate at 100% which means that THIS game is cpu limited.I'm not really sure but I think my gpu does not have any problems regarding performance on ppsspp)

I know multithreading at least functions on bcm28155 since the issues that appear only when MT is on also appears on my device.But thing is like I have said,it does not fuction properly.

Thank you very much anyways

[mckimiaklopa]

Some comparison to between the performance of bcm28155:
(all have buffered rendering on w/ auto frameskip at 2 using Tekken DR)
1.2 ghz quadcore cortex-a7 with Adreno 203
Multithreading OFF
11/60(60 %)
MT On
11/60(100%)

1.0 ghz dual core cortex-a9 with power vr sgx 531

MT OFF
15/60(60%)

MT ON
20/60(100%)

bcm28155
1.2 ghz dual core cortex-a9 with videocore IV HW gpu

MT off
20/60(80%)
MT ON
20/60(80%)

the first has some benefits with multithreading but on bcm28155,there are no changes

[mckimiaklopa]

#5627

[hrydgard]

We are not doing anything special with multithreading for specific chips. All we are doing is using standard pthreads, and it's up to the platform kernel to do something sensible with the threads. If the Android OS running on these devices fails to do so, perhaps due to lousy power management code, it's not the fault of PPSSPP - although I'm sure there are cases where we can do things slightly better, there's nothing to do for specific devices.

Hence, this stays closed. If you have an idea how to fix it, that's different.

[hrydgard]

Also it's important to realize that most of these devices are not tuned to run multithreaded game code efficiently, they are tuned to minimize power consumption at all costs. This is good for regular users who don't use emulators or run heavy games, but bad for us of course. There's nothing we can do about it really.

[mckimiaklopa]

umm,explain more please,cause i don't see how it really helps in shedding light to the problem or how it makes bcm28155 different from other chips(I really do not understand it)Since you have already done specific fixes for power vr,MALI,Nvidia ,Adreno ,AMD,maybe it'll be nice to at least investigate this.
I'll also try to investigate
also,just for reference #3116

[mckimiaklopa]

How does ppsspp utilize multithreading?maybe this can connect to how bcm28155 chips use multithreading.As far as searching goes,all apps that utilizes the dual core of my device do it perfectly without a hitch.Maybe there is just something different with ppsspp that does not automatically make my device go through perfect multithreading

[mckimiaklopa]

I think I have proven that there is indeed a problem with multithreading on BCM28155 chip.
I installed on my phone a backup of ppsspp 0.9.1-2300 which I have installed in the past to my other devices.With multithreading on,There are huge bugs on the internal framerate(note thnat cpu clock is set to default)
1.With MT on in this build,The first loading screen in TEKKEN DARK RESSURECTION has an internal FPS of 4 and it'll eventually go to 0.IF i unthrottle and go to a battle,the internal framerate is 20 fps 0r less.
2.On kingdom hearts birth by sleep,the new game screen,instead of having a 60 fps internal fps,the framerate is 30 internally!!!!
On actual gameplay,framerate is 17 fps internally(thats on enchanted dominion using terra) plus there are screen flickering even though frameskip and buffered rendering are on/off

Turning multithreading OFF will fix the above issu
I have installed ppsspp 0.9.1-2300 on my power vr device,my friend's snapdragon device,my sister's Mali device and my dad's intel pentium dual core device and all had stable internal fps with multithreading ON.

Off course,the above issues are gone on the current build,but it has something to do with multithreading having no functionality on BCM28155 and this leads me to belive that it has something to to with cpu/gpu/ge timing on the said chipset