Good idea - will do the same kernel and test without Jailhouse to compare. Thanks all
On Feb 23, 2017 7:24 PM, "Ralf Ramsauer" <[email protected]> wrote: > On 02/23/2017 08:17 AM, Henning Schild wrote: > > On Thu, 23 Feb 2017 06:00:15 -0800 > > Dan Zach <[email protected]> wrote: > > > >> Dear forum, > >> > >> On the Jetson TK1 inmate I use linux 4.8.2 with PREEMPT-RT patch. > >> I measure a 1KHz high priority task based on hrtimer events that > >> measures it's own jitter. > Run jailhouse cell stats for your RT-cell and watch the MMIO traps. I > guess it will heavily trap on RT. RT heavily accesses the GICD that > needs to be emulated in hardware > >> > >> The worst case, I get 400uS jitter on 1mS tick - not so bad, but the > Uh, okay? With the root cell idling? CONFIG_HZ_1000? > > Uhm -- What's your clocksource? Could you please post /proc/timer_list? > >> interesting thing is that the jitter stays as low as 50uS, untill I > >> start activity on the root cell, especially GUI. > >> > >> So the questions is: if the non-root cell is completely isolated from > >> the root: separate physical memory, PPI from its local timer, where > >> this cross influence can come from? > > > > Well the cells are not completely isolated, some shared resources > > remain. The jitter you are seeing is caused by those, i.e. caches and > > busses. And GPU workloads would likely stress exactly those. > Yep, mainly shared system bus and caches. Others like MMIO dispatching > and IRQ reinjection cause (at least measurable) latencies. I already did > some measurements to get worst case latencies, but I never hit anything > like that, interestingly. > > Do those latencies also occur if you use an Preempt-RT patched kernel > without Jailhouse when the GPU gets stressed? > > Ralf > > > > Henning > > > >> Thanks > >> Dan > >> > > > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Jailhouse" group. > To unsubscribe from this topic, visit https://groups.google.com/d/ > topic/jailhouse-dev/RfucfkcbNQU/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
