On Mon, Oct 11, 2010 at 10:00 PM, Jack Daniel <[email protected]> wrote: > On Thu, Oct 7, 2010 at 8:30 PM, wu zhangjin <[email protected]> wrote: >> Hi, Jack >> >> On 10/7/10, Jack Daniel <[email protected]> wrote: >>> Hi Wu, >>> >>> I was going through your latency tracing implementation for loongson. >>> Could you please assist me in understanding the following. >>> >>> 1) How is the latency tracing implemented here different from ftrace >>> tracer function "irqsoff" ? "irqsoff" calculates the time when >>> interrupts are disabled. >> >> What do you mean "the latency tracing implemented here"? In reality, >> the latency tracers I have used are the ones you said above: irqsoff >> tracer, preemptoff tracer and preemptirqsoff tracer, wakeup tracer ... > > My apologies for not articulating my question properly. What I meant > was the latency tracing support available at > Device Drivers ---> [*] PREEMPT_RT Specific Device Drivers ---> > <*> Interrupt Latency Driver > I see that you are the only one to support this in your tree for > loongson. How different is this from "irqsoff" supported by Ftrace? >
The "Interrupt latency driver" differs from the irqsoff tracer, it tries to measure the time between the interrupt emitted and the interrupt is really handled, it reflects the response time of an interrupt. Perhaps you can write such one driver for octeon via the RTC driver (if your board has such a driver) for we can use RTC to generate interrupt, For Loongson, I have used the MFGPT timer. Regards, Wu Zhangjin >> >> But at the time I was using them, they didn't work well for they could >> not provide high resolution timestamp: The unit of the timestamp >> resolution is only ms, so, the latency result is always >= 1000 us, >> which can not reflect the real situation of the latencies. Therefore, >> I have tried to fix it via adding the high resolution sched_clock() >> support. >> >>> >>> 2) Could you give me a reference or guide on how to implement the same >>> for another mips platform such as Octeon? >> >> Which kernel version are you using? For the latest kernel versions, >> the latency tracers should be supported very well except the high >> resolution sched_clock(). For Octeon, the support of high resolution >> sched_clock() has already been there from 2.6.33, but for the r4k >> MIPS, you may need to apply the patches from the patchwork of >> linux-mips: >> >> http://patchwork.linux-mips.org/patch/1102/ >> http://patchwork.linux-mips.org/patch/1104/ > > Thank you for this tip, I will take a look. > > Regards, > Jack. > -- You received this message because you are subscribed to the Google Groups "loongson-dev" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/loongson-dev?hl=en.
