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kernelOfTruth
Watchman
Watchman


Joined: 20 Dec 2005
Posts: 6102
Location: Vienna, Austria; Germany; hello world :)

PostPosted: Fri Jul 10, 2015 8:26 pm    Post subject: Realtime & Low-latency scheduling (Gaming, Pro-Audio, et Reply with quote

Hi guys,


[WIP]

This is mainly a stub for now and is mostly tailored towards CFS



here's a incomplete list of settings to set up to get a nice low-latency response from your system.


The intention to get this kind of behavior can be to do Gaming on Linux - either native (e.g. via Steam) or WINE (e.g. Crysis, Mass Effect 3 [with or without MultiPlayer], etc.)


or tasks that require that the system is processing load in a deadline-like fashion.



kernel-related settings:

run the kernel with

threadirqs

appended to your bootloader


For CFS (classical, vanilla) CPU scheduler

Code:
zgrep GROUP /proc/config.gz
CONFIG_CGROUPS=y
CONFIG_CGROUP_DEBUG=y
CONFIG_CGROUP_FREEZER=y
# CONFIG_CGROUP_DEVICE is not set
CONFIG_CGROUP_CPUACCT=y
# CONFIG_CGROUP_HUGETLB is not set
CONFIG_CGROUP_PERF=y
CONFIG_CGROUP_SCHED=y
CONFIG_FAIR_GROUP_SCHED=y
CONFIG_RT_GROUP_SCHED=y
CONFIG_BLK_CGROUP=y
# CONFIG_DEBUG_BLK_CGROUP is not set
CONFIG_SCHED_AUTOGROUP=y
CONFIG_CFQ_GROUP_IOSCHED=y
CONFIG_CGROUP_BFQIO=y



For BFS (tweaked, aka "beefy") CPU scheduler

...

fixme



Scheduler behavior related changes (general):


General scheduler changes for CFS:

Code:
echo "6000000" > /proc/sys/kernel/sched_latency_ns
echo "100000" > /proc/sys/kernel/sched_min_granularity_ns
echo "10000" > /proc/sys/kernel/sched_wakeup_granularity_ns
echo "7000000" > /proc/sys/kernel/sched_migration_cost_ns
echo "8" > /proc/sys/kernel/sched_nr_migrate
echo "80000" > /proc/sys/kernel/sched_shares_window_ns
echo "970000" > /proc/sys/kernel/sched_rt_runtime_us
echo "1000000" > /proc/sys/kernel/sched_rt_period_us



General scheduler changes for BFS:

Code:
echo "4" > /proc/sys/kernel/rr_interval
echo "85" > /proc/sys/kernel/iso_cpu





IRQ-related tweaking:


Sample:


Code:
#!/bin/bash

# Sorted view:
# ps -eLo rtprio,cls,pid,pri,nice,cmd | grep "FF" | sort -r

# ps -eLo pid,cls,rtprio,pri,nice,cmd | grep -i "irq"

# For a non-RT kernel, use kernel option: threadirqs

# http://subversion.ffado.org/wiki/IrqPriorities
# http://alsa.opensrc.org/Rtirq

#piwl=$(pgrep "irq/.*-iwlwifi")
#[[ -n $piwl ]] && chrt -f -p 10 $piwl

#peth=$(pgrep "irq/.*-eth0")
#[[ -n $peth ]] && chrt -f -p 30 $peth

#peth=$(pgrep "irq/.*-eth1")
#[[ -n $peth ]] && chrt -f -p 30 $peth

peth=$(pgrep "irq/.*-eth")
[[ -n $peth ]] && chrt -f -p 50 $peth

# ehci instead of uhci
pmouse=$(pgrep "irq/23-ehci")
[[ -n $pmouse ]] && chrt -f -p 59 $pmouse

pmouse=$(pgrep "irq/20-ehci")
[[ -n $pmouse ]] && chrt -f -p 59 $pmouse

#pmouse=$(pgrep "irq/19-uhci")
#[[ -n $pmouse ]] && chrt -f -p 59 $pmouse

psnd=$(pgrep "irq/.*-snd_")
[[ -n $psnd ]] && chrt -f -p 85 $psnd

#pnouveau=$(pgrep "irq/.*-nouveau")
#[[ -n $pnouveau ]] && chrt -f -p 80 $pnouveau

pnvkm=$(pgrep "irq/.*-nvkm")
[[ -n $pnvkm ]] && chrt -f -p 84 $pnvkm

pnvidia=$(pgrep "irq/.*-nvidia")
[[ -n $pnvkm ]] && chrt -f -p 84 $pnvidia


#pkbd=$(pgrep "irq/.*-i8042")
## 2 of them
#for p in $pkbd ; do
#   chrt -f -p 60 $p
#done

prtc=$(pgrep "irq/.*-rtc0")
[[ -n $prtc ]] && chrt -f -p 90 $prtc

#( while true ; do
#   # Does not have an IRQ until Xorg is running
#   pnvidia=$(pgrep "irq/.*-nvidia")
#   if [[ -n $pnvidia ]] ; then
#      chrt -f -p 80 $pnvidia
#      break
#   fi
#   sleep 20
#done ) &



priority for the nvidia kernel-module doesn't seem to get changed thus - I'll usually do it manually:


Code:
ps -eLo rtprio,cls,pid,pri,nice,cmd | grep "FF" | sort -r


<-- look for nvidia

Quote:
50 FF 13613 90 - [irq/39-nvidia]


so

Code:
chrt -f -p 84 13613




software-related tweaking:

Giving the X-server some more bite:

Code:
chrt -a -p -r 9 `pidof X`



check in htop or top afterwards whether priority got raised to -10



Gaming and app-related tweaking:


Running WINE ?


Code:
schedtool -R -p 90 $(pidof wineserver)




and on top of that Mass Effect 3 Multiplayer ?


Code:
ps aux | grep MassEffect3.exe


Does it e.g. reveal 15436 as PID ?


Code:
chrt -a -p -r 89 15436




WINE-related considerations:


Make sure to emerge WINE with the staging-USE-flag

and enable CSMT-support in winecfg




Results:


(especially)
Mass Effect 3 Multiplayer

and

Borderlands2


run way much smoother than before !


Borderlands runs flawlessly (at least the native port launched from within Steam)


and


ME3 MP runs 75-95% (in my impression) at speed.

You might need to disable dynamic shadows and AA, do a little tweaking in the GameSettings.ini

but overall it runs surprisingly well.

1920x1080 vs. 1920x1080 in Windows


Whereas previously I couldn't bear to do several rounds on Linux - so only as a occasional bite

it now could prevent me from booting into Windows :wink:



Acknowledgements:

- PaulBredbury https://forums.gentoo.org/viewtopic-p-7153966.html#7153966
You ROCK :D

- Rookie1337 http://www.overclock.net/t/1519964/experiment-overclocking-the-linux-os-through-the-sysclt-proc-sys-sys-block-and-other-settings#post_23094293
That's some sick well-documented shift :mrgreen:

- All Gentooligans
Ricers UNITE ! :P
_________________
https://github.com/kernelOfTruth/ZFS-for-SystemRescueCD/tree/ZFS-for-SysRescCD-4.9.0
https://github.com/kernelOfTruth/pulseaudio-equalizer-ladspa

Hardcore Gentoo Linux user since 2004 :D
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joe4379
n00b
n00b


Joined: 19 Jan 2015
Posts: 7

PostPosted: Thu Dec 01, 2016 4:38 pm    Post subject: thanks, and a script Reply with quote

Thanks! This is huge! :twisted:

I made a script to semi-automate setting the Nvidia priority (nothing to remember at least). It has sudos and i dont care...

Code:
  GNU nano 2.7.1                                                        File: /usr/bin/tweaks                                                                 

sudo chrt -a -p -r 9 `pidof X`

#[[ -n $pnvkm ]] && chrt -f -p 84 $pnvidia
ps -eLo rtprio,cls,pid,pri,nice,cmd | grep "FF" | sort -r |grep nvidia
echo "What's the third number (PID of nVidia IRQ)?"
read -e PIDOFNVIDIA
sudo chrt -f -p 84 $PIDOFNVIDIA
chrt -p $PIDOFNVIDIA

echo "100000" | sudo tee /proc/sys/kernel/sched_latency_ns
echo "100000" | sudo tee /proc/sys/kernel/sched_min_granularity_ns
echo "1000" | sudo tee /proc/sys/kernel/sched_wakeup_granularity_ns
echo "25000" | sudo tee /proc/sys/kernel/sched_migration_cost_ns
echo "4" | sudo tee /proc/sys/kernel/sched_nr_migrate
echo 1024 | sudo tee /proc/sys/kernel/msgmax && echo 2048 | sudo tee /proc/sys/kernel/msgmnb && echo 8192 | sudo tee /proc/sys/kernel/msgmni
echo "990000" | sudo tee /proc/sys/kernel/sched_rt_runtime_us
echo "1000000" | sudo tee /proc/sys/kernel/sched_rt_period_us
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timofonic
n00b
n00b


Joined: 13 Sep 2005
Posts: 16

PostPosted: Sun Dec 11, 2016 12:59 pm    Post subject: Re: thanks, and a script Reply with quote

Hello.

Nvidia proprietary support for this? Thanks a lot! My laptop will be very happy (I plan to install Gentoo on a laptop, I'll have a big workstation later).

It could be nice to standarize the process, make a github.com repository and a package and publish it in Gentoo wiki. This way, realtime and low latency could be more easily adopted. Even better, a database of tweaks for different apps could be made and including Wine software too.

Really: Why isn't realtime and low latency options part of a default Linux desktop installation? I tired it a few times and the results are amazing from my point of view, but the process is really quite cumbersome.

Kind regards.

Code:
/usr/bin/tweaks


joe4379 wrote:
Thanks! This is huge! :twisted:

I made a script to semi-automate setting the Nvidia priority (nothing to remember at least). It has sudos and i dont care...

Code:
                                                                 
sudo chrt -a -p -r 9 `pidof X`

#[[ -n $pnvkm ]] && chrt -f -p 84 $pnvidia
ps -eLo rtprio,cls,pid,pri,nice,cmd | grep "FF" | sort -r |grep nvidia
echo "What's the third number (PID of nVidia IRQ)?"
read -e PIDOFNVIDIA
sudo chrt -f -p 84 $PIDOFNVIDIA
chrt -p $PIDOFNVIDIA

echo "100000" | sudo tee /proc/sys/kernel/sched_latency_ns
echo "100000" | sudo tee /proc/sys/kernel/sched_min_granularity_ns
echo "1000" | sudo tee /proc/sys/kernel/sched_wakeup_granularity_ns
echo "25000" | sudo tee /proc/sys/kernel/sched_migration_cost_ns
echo "4" | sudo tee /proc/sys/kernel/sched_nr_migrate
echo 1024 | sudo tee /proc/sys/kernel/msgmax && echo 2048 | sudo tee /proc/sys/kernel/msgmnb && echo 8192 | sudo tee /proc/sys/kernel/msgmni
echo "990000" | sudo tee /proc/sys/kernel/sched_rt_runtime_us
echo "1000000" | sudo tee /proc/sys/kernel/sched_rt_period_us
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