Am Fri, 23 Jun 2017 14:56:58 -0700 schrieb Gustavo Lima Chaves <[email protected]>:
> * Jan Kiszka <[email protected]> [2017-06-23 22:36:35 +0200]: > > > On 2017-06-23 19:33, Gustavo Lima Chaves wrote: > > > [...] > > > > > >>> > > >>> When I artificially block this interrupt after a while, I see > > >>> the real time jitter behaving almost perfectly. > > >>> > > >>> > > >>> Can you see how interrupt SPI storm ,though to the root cell, > > >>> might damage RT jitter on another cell? > > >> > > >> The interrupt storm may be just one symptom of load on shared > > >> resources. Maybe the GPU or its driver are also issuing a high > > >> load of memory accesses or are otherwise stressing the shared > > >> interconnects. > > >> > > >> Looking at the hypervisor, there should be no interference > > >> between two cells if one receives lots of interrupts. > > >> Specifically, there is only one shared lock between both in > > >> irqchip.c (dist_lock), but it's taken only for a very short > > >> read-modify-write access. > > >> > > >> Jan > > > > > > What about Linux inmate cells on Intel? Has anybody else seem > > > horrid timer resolutions (like ".resolution: 1000000 nsecs") as > > > well? The aforementioned ARM patch makes no sense for the x86's > > > version of time.c, I guess. Should we be providing HPET address > > > to the inmate the same way it's done for PM timer address? Any > > > other ideas? > > > > What's your setup exactly? > > Maybe it's something in my inmate Linux config? I've tried with two > codebases there: RT Linux and upstream (both with Jailhouse patches, > naturally). I'll attach one of the configs. > > > > > There is no need to use the slow HPET on x86 anymore, with or > > without Jailhouse. We now have the local APIC as reliable > > high-resolution and high-performance (because it's core-local) > > timer. > > OK, fair. Still wondering what's giving that final bad resolution. The > rest of the setup is a Fedora 25 system on QEMU, kernel 4.8, with > pristine qemu-vm and linux-x86-demo cells running. So you are running Jailhouse and the rt-preempt non-root cell on qemu? Getting solid rt-performance there might be tricky, that should not be your starting point when looking at realtime! Henning > > > > And as reference clock, the PM timer is easily and cleanly exported > > to inmates - that's why we do that. > > OK, I'll keep searching the source of that strange behavior, thanks. > > > > > Jan > > > > -- > > Siemens AG, Corporate Technology, CT RDA ITP SES-DE > > Corporate Competence Center Embedded Linux > > > > -- > > 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. > -- 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.
