> Subject: Re: jailhouse jitter? > > On 27.07.20 08:56, Peng Fan wrote: > >> Subject: Re: jailhouse jitter? > >> > >> On 27.07.20 08:25, Peng Fan wrote: > >>> Hi Jan > >> > >> ... > >> > >>> > >>> I tested the SDEI on i.MX8MM, it shows the jitter became smaller. > >>> > >>> Without SDEI, the gic-demo jitter is 999ns+ With SDEI, the gic-demo > >>> jitter is 124ns~246ns. > >>> > >>> Indeed no more vmexits. > >>> > >>> But the max jitter, some times SDEI bigger only when program start > >>> up, > >> mostly because of CACHE WARM UP I think. > >> > >> That is one source. If you add a warm-up period, they can be > >> mitigated, though. > >> > >> The other source might be last-level cache sharing. If there are > >> cache-miss counters, maybe you can check if those increase along the > peaks. > > > > Yes. When I add stress-ng in root cell, the jitter became larger sometimes. > > > > I've seen the same on the ultra96. My cache theory should be validated, > though, because I would have assumed that all of the gic demo fits into a > core-local cache.
After thinking more about root cell color, when booting jailhouse before Linux. We are not using 1:1 mapping anymore or we could use 1:1 mapping with many pieces of small ram area. So I think the first 1 is better, but when use kmalloc for dma usage sometimes, it will bring issues, because not 1:1 mapping, unless we let all drivers use dedicated dma area reserved and not colored. > > > > >> > >>> > >>> Will you move SDEI support to jailhouse mainline? > >> > >> Once the to-dos are addressed. Any contributions? > > > > I'll read more into your patches and check the to-dos you listed in > > the jailhouse commit log to see what I could help there. > > > > Item one (SDEI probing) is almost resolved. > > >> > >> BTW, did you have to patch ATF for your experiment? Will you upstream > >> that patch? > > > > Yes. I'll upstream that. Quite simple, I only enabled one SDEI private > > event. > > > > Perfect. Sent out. https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/5116 Thanks, Peng. > > Jan > > -- > Siemens AG, Corporate Technology, CT RDA IOT 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/DB6PR0402MB276063FAB38B540E81ED7D3288700%40DB6PR0402MB2760.eurprd04.prod.outlook.com.
