[Xenomai] How to locate the max latency

Greg Gallagher greg at embeddedgreg.com
Wed Jul 4 13:10:35 CEST 2018


Did youale any changes in menuconfig when building the kernel?

Greg

  Original Message  
From: qi.zheng at intel.com
Sent: July 4, 2018 3:27 AM
To: xenomai at xenomai.org
Subject: [Xenomai] How to locate the max latency

BTW, I already disabled the i915 power saving by adding "i915.enable_dc=0 i915.enable_rc6=0 i915.enable_execlists=0 i915.disable_power_well=0" in  the cmdline.

Best Regards

SSG->OTC->One Linux Platform Engineering Team (Shanghai)

From: Zheng, Qi
Sent: Tuesday, July 3, 2018 5:00 PM
To: xenomai at xenomai.org
Subject: How to locate the max latency

I am using xenomai 3.0.5 (https://xenomai.org/downloads/xenomai/stable/xenomai-3.0.5.tar.bz2) on the Intel SKL platform.
On console mode or accessed by vnc viewer (no i915 graphics interrupt), the max latency values are usually below 20us no matter low or high loading (by stress-ng).
But the max latency can reach up to 40us on GUI (gnome)  mode (dozens of i915 interrupt counts per second).
I tried enabling the ipipe trace function, but couldn't find valuable information.
Is there any other good ways to locate the max latency?
Or does anybody have experience on reducing the latency caused by graphics (such as i915) ?
Many thanks.


Best Regards

SSG->OTC->One Linux Platform Engineering Team (Shanghai)

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