Re: v0.9 vs v1.1 interrupt latency raise
On 25.10.19 15:52, Henning Schild wrote: > Well you only have soo many shared ressources and if it is not > additional exits/interrupts then it is contention on shared ressources. > > We are probably talking about caches, TLBs and buses. > > You should be able to use i.e. "perf" on Linux to read out hardware > performance counters. And there you might want to look for TLB and > cache misses. > > But the bisecting might be the better idea. Jan already mentioned the > "features" that could be responsible. With a bit of educated guessing > you will get away with just a few tries. BTW, does your RTOS happen to use anything of the inmate bootstrap code to start in Jailhouse? That also changed. Jan > > Henning > > Am Fri, 25 Oct 2019 00:04:36 -0700 > schrieb Chung-Fan Yang : > >> Alright, I have test the latency from HW IRQ to application response. >> >> I found out that there aren't any additional VM-Exit or IRQ, nor RTOS >> scheduling and house-keeping. >> >> It feels like the processor is generally slower as everything takes >> longer to run. >> >> The IRQ epilogue takes ~7.8us and iretq ~2.x us. In addition, the >> libc and syscall interface also have slow downed a bit. >> >> I do notice after upgrading, even with CAT, my RTOS latency are prone >> to be influenced by the Linux side applications. >> This was not observed during v0.9.1. >> >> It's strange. >> >> >> Yang. >> > > > -- 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 jailhouse-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/76ecfa10-3a69-b5bc-382a-48a59c345637%40siemens.com.
Re: v0.9 vs v1.1 interrupt latency raise
Well you only have soo many shared ressources and if it is not additional exits/interrupts then it is contention on shared ressources. We are probably talking about caches, TLBs and buses. You should be able to use i.e. "perf" on Linux to read out hardware performance counters. And there you might want to look for TLB and cache misses. But the bisecting might be the better idea. Jan already mentioned the "features" that could be responsible. With a bit of educated guessing you will get away with just a few tries. Henning Am Fri, 25 Oct 2019 00:04:36 -0700 schrieb Chung-Fan Yang : > Alright, I have test the latency from HW IRQ to application response. > > I found out that there aren't any additional VM-Exit or IRQ, nor RTOS > scheduling and house-keeping. > > It feels like the processor is generally slower as everything takes > longer to run. > > The IRQ epilogue takes ~7.8us and iretq ~2.x us. In addition, the > libc and syscall interface also have slow downed a bit. > > I do notice after upgrading, even with CAT, my RTOS latency are prone > to be influenced by the Linux side applications. > This was not observed during v0.9.1. > > It's strange. > > > Yang. > -- Siemens AG Corporate Technology CT RDA IOT SES-DE Otto-Hahn-Ring 6 81739 Muenchen, Germany Mobile: +49 172 8378927 mailto: henning.sch...@siemens.com -- 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 jailhouse-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/20191025155257.6af12e29%40md1za8fc.ad001.siemens.net.
Re: v0.9 vs v1.1 interrupt latency raise
Alright, I have test the latency from HW IRQ to application response. I found out that there aren't any additional VM-Exit or IRQ, nor RTOS scheduling and house-keeping. It feels like the processor is generally slower as everything takes longer to run. The IRQ epilogue takes ~7.8us and iretq ~2.x us. In addition, the libc and syscall interface also have slow downed a bit. I do notice after upgrading, even with CAT, my RTOS latency are prone to be influenced by the Linux side applications. This was not observed during v0.9.1. It's strange. Yang. -- 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 jailhouse-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/48bb5fe2-9b9f-4ad1-872e-9eae4bdd2c43%40googlegroups.com.
