Why X11 influences the latency of xenomai？

Why X11 influences the latency of xenomai？

[孙世龙]

Hi,
    Why X11 influences the latency of xenomai？I guess it has some relation
to GPU.Could you make me more clearly?
    I have solved the latency . I am using QT runing on linux framebuffer
,disabled X11 at all.I really hope to why  X11 influences the latency of
xenomai
    Thanks a lot.Looking forward to your reply.
    Best regards.

Re: Why X11 influences the latency of xenomai？

[Jan Kiszka]

On 08.04.20 10:39, 孙世龙 via Xenomai wrote:
> Hi,
>      Why X11 influences the latency of xenomai？I guess it has some relation
> to GPU.Could you make me more clearly?
>      I have solved the latency . I am using QT runing on linux framebuffer
> ,disabled X11 at all.I really hope to why  X11 influences the latency of
> xenomai

It's not X11, it's the side effects of certain GPU usage patterns on 
your particular platform. Can you specify more details about both?

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

Re: Why X11 influences the latency of xenomai？

[孙世龙]

Hi,
      I could not catch your idea about the GPU usage patterns. How could
I acquire this information?

      My laptop model is Dell Latitude 5501 runing over ubuntu 14.04 system.
      GPU model information： NVIDIA GeForce MX150.

     Best regards.

Jan Kiszka <jan.kiszka@siemens.com> 于2020年4月8日周三 下午5:05写道：

> On 08.04.20 10:39, 孙世龙 via Xenomai wrote:
> > Hi,
> >      Why X11 influences the latency of xenomai？I guess it has some
> relation
> > to GPU.Could you make me more clearly?
> >      I have solved the latency . I am using QT runing on linux
> framebuffer
> > ,disabled X11 at all.I really hope to why  X11 influences the latency of
> > xenomai
>
> It's not X11, it's the side effects of certain GPU usage patterns on
> your particular platform. Can you specify more details about both?
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> Corporate Competence Center Embedded Linux
>

Re: Why X11 influences the latency of xenomai？

[Jan Kiszka]

On 08.04.20 15:13, 孙世龙 wrote:
> Hi,
>        I could not catch your idea about the GPU usage patterns. How 
> could I acquire this information?
>        My laptop model is Dell Latitude 5501 runing over ubuntu 14.04 
> system.
>        GPU model information： NVIDIA GeForce MX150.
> 

NVIDIA... using their close-source driver or nouveau?

It's been a long time I ran that on a Xenomai box, I only vaguely 
remember that there used to be issues with lengthy cache flushes when 
data is pushed to RAM in order to make it visible to the GPU.

Jan

>       Best regards.
> 
> Jan Kiszka <jan.kiszka@siemens.com <mailto:jan.kiszka@siemens.com>> 于 
> 2020年4月8日周三 下午5:05写道：
> 
>     On 08.04.20 10:39, 孙世龙 via Xenomai wrote:
>      > Hi,
>      >      Why X11 influences the latency of xenomai？I guess it has
>     some relation
>      > to GPU.Could you make me more clearly?
>      >      I have solved the latency . I am using QT runing on linux
>     framebuffer
>      > ,disabled X11 at all.I really hope to why  X11 influences the
>     latency of
>      > xenomai
> 
>     It's not X11, it's the side effects of certain GPU usage patterns on
>     your particular platform. Can you specify more details about both?
> 
>     Jan
> 
>     -- 
>     Siemens AG, Corporate Technology, CT RDA IOT SES-DE
>     Corporate Competence Center Embedded Linux
> 


-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

Re: Why X11 influences the latency of xenomai？

[Alec Ari]

I have seen latency spikes caused by things in X with all DRM/KMS drivers disabled, only using xf86-video-vesa with Mesa software rasterizer. X can cause spikes without any GPU involvement, and I'm interested in this subject as well.

Alec

RE: Why X11 influences the latency of xenomai？

[Meng, Fino]

On 08.04.20 10:39, 孙世龙 via Xenomai wrote:
> Hi,
>     Why X11 influences the latency of xenomai？I guess it has some relation to
> GPU.Could you make me more clearly?
>     I have solved the latency . I am using QT runing on linux
> framebuffer ,disabled X11 at all.I really hope to why  X11 influences the
> latency of xenomai
>     Thanks a lot.Looking forward to your reply.
>     Best regards.

GPU do have big impact; use headless (without GUI) Linux if possible. 
If your app really need cobalt thread and 3D graphics running together, 
On x86_64 you can try CAT (cache allocation technology)

https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/cache-allocation-technology-white-paper.pdf
https://github.com/intel/intel-cmt-cat


BR / Fino (孟祥夫)
Intel – IOTG Developer Enabling

RE: Why X11 influences the latency of xenomai？

[Meng, Fino]

> I have seen latency spikes caused by things in X with all DRM/KMS drivers
> disabled, only using xf86-video-vesa with Mesa software rasterizer. X can
> cause spikes without any GPU involvement, and I'm interested in this subject
> as well.
> 
> Alec

If BIOS has the items, you can try set GPU frequency to minimum(100Mhz).
But if your app really need a better graphics performance, 
CAT (cache allocation tech.) will help to improve realtime capability on x86_64 processor, 

BR / Fino (孟祥夫)
Intel – IOTG Developer Enabling

Re: Why X11 influences the latency of xenomai？

[Alec Ari]

I'm thinking it's worth as a troubleshooting step to remove the GPU, no graphics at all (nor integrated) and do graphics completely over USB and see if those spikes come back.

Alec

Re: Why X11 influences the latency of xenomai？

[Pierre FICHEUX]

GPU is not RT friendly.
We did several tests for several projects with/without using GPU and
latencies are about 2x higher with GPU.

Here is a discussion with Philippe in 2015 (translated from french) :

"With a GPU, it is often the X driver that has hard IRQ masking sections.
In addition, GPU tend to cause stalls, to optimize traffic on their side,
but not ours.
Then there are the unbreakable cache maintenance instructions sometimes
used by the kernel to manage consistency with the GPU. In short, for sure,
the latency is higher"

Regards


Le jeu. 9 avr. 2020 à 06:20, Alec Ari via Xenomai <xenomai@xenomai.org> a
écrit :

> I'm thinking it's worth as a troubleshooting step to remove the GPU, no
> graphics at all (nor integrated) and do graphics completely over USB and
> see if those spikes come back.
>
> Alec
>
>

-- 

Pierre FICHEUX -/- CTO Smile ECS, France -\- pierre.ficheux@smile.fr
                             http://www.smile.fr
                             https://smile.eu/fr/offres/embarque-iot
I would love to change the world, but they won't give me the source code

RE: Why X11 influences the latency of xenomai？

[Meng, Fino]

> 
> I'm thinking it's worth as a troubleshooting step to remove the GPU, no
> graphics at all (nor integrated) and do graphics completely over USB and see
> if those spikes come back.
> 
> Alec

We have discuss with approach;
but our users usually need to draw 3D when they need GUI; pure CPU 3D lib is not mainstream.

BR / Fino (孟祥夫)
Intel – IOTG Developer Enabling

Re: Why X11 influences the latency of xenomai？

[孙世龙]

Hi,
    I am using nouveau.The related log is listed below.
    GPU model is NVIDIA GeForce GT 650M which was manufactured 9 years
ago.I also do the same test on NVIDIA GK107M which was mentioned in last
letter.
    Sombody claims that they have killed the latency by using nouveau.
    While I using X11 on my laptop, the latency is still a problem.I have
modified the config file for X11 following the guideline on the xenomai
wifi.

Best regards.

sun@sun-Lenovo-IdeaPad-Y480:~$ lspci -nnk | grep -iA2 vga
00:02.0 VGA compatible controller [0300]: Intel Corporation 3rd Gen Core
processor Graphics Controller [8086:0166] (rev 09)
Subsystem: Lenovo 3rd Gen Core processor Graphics Controller [17aa:3977]
Kernel driver in use: i915
--
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK107M
[GeForce GT 650M] [10de:0fd1] (rev a1)
Subsystem: Lenovo GK107M [GeForce GT 650M] [17aa:3977]
Kernel driver in use: nouveau
sun@sun-Lenovo-IdeaPad-Y480:~$


joy@joy-Lenovo-IdeaPad-Y480:~$ lspci -nnk | grep -iA2 vga
00:02.0 VGA compatible controller [0300]: Intel Corporation 3rd Gen Core
processor Graphics Controller [8086:0166] (rev 09)
Subsystem: Lenovo 3rd Gen Core processor Graphics Controller [17aa:3977]
Kernel driver in use: i915
--
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK107M
[GeForce GT 650M] [10de:0fd1] (rev a1)
Subsystem: Lenovo GK107M [GeForce GT 650M] [17aa:3977]
Kernel driver in use: nouveau
joy@joy-Lenovo-IdeaPad-Y480:~$

Jan Kiszka <jan.kiszka@siemens.com> 于2020年4月9日周四 上午12:41写道：

> On 08.04.20 15:13, 孙世龙 wrote:
> > Hi,
> >        I could not catch your idea about the GPU usage patterns. How
> > could I acquire this information?
> >        My laptop model is Dell Latitude 5501 runing over ubuntu 14.04
> > system.
> >        GPU model information： NVIDIA GeForce MX150.
> >
>
> NVIDIA... using their close-source driver or nouveau?
>
> It's been a long time I ran that on a Xenomai box, I only vaguely
> remember that there used to be issues with lengthy cache flushes when
> data is pushed to RAM in order to make it visible to the GPU.
>
> Jan
>
> >       Best regards.
> >
> > Jan Kiszka <jan.kiszka@siemens.com <mailto:jan.kiszka@siemens.com>> 于
> > 2020年4月8日周三 下午5:05写道：
> >
> >     On 08.04.20 10:39, 孙世龙 via Xenomai wrote:
> >      > Hi,
> >      >      Why X11 influences the latency of xenomai？I guess it has
> >     some relation
> >      > to GPU.Could you make me more clearly?
> >      >      I have solved the latency . I am using QT runing on linux
> >     framebuffer
> >      > ,disabled X11 at all.I really hope to why  X11 influences the
> >     latency of
> >      > xenomai
> >
> >     It's not X11, it's the side effects of certain GPU usage patterns on
> >     your particular platform. Can you specify more details about both?
> >
> >     Jan
> >
> >     --
> >     Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> >     Corporate Competence Center Embedded Linux
> >
>
>
> --
> Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> Corporate Competence Center Embedded Linux
>

Re: Why X11 influences the latency of xenomai?

[孙世龙]

Hi,
     I am interested that how to disable all DRM/KMS drivers while the
functions of X ares not inflenced?

     I am surprised that  X can cause spikes without any GPU
involvement.It's amazing!

    Thanks a lot.Looking for your reply.

    Best regards.

>>From: Alec Ari <neotheuser@ymail.com>
>>To: Jan Kiszka <jan.kiszka@siemens.com>, Xenomai <xenomai@xenomai.org>
>>Subject: Re: Why X11 influences the latency of xenomai？
>>Message-ID: <1696334749.1963937.1586394200231@mail.yahoo.com>
>>Content-Type: text/plain; charset=UTF-8

>>I have seen latency spikes caused by things in X with all DRM/KMS drivers
>>disabled, only using xf86-video-vesa with Mesa software rasterizer. X can
cause >>spikes without any GPU involvement, and I'm interested in this
subject as well.

>>Alec