Messages in this thread | | | Subject | Re: Latency data - 2.6.14-rc3-rt13 | From | Daniel Walker <> | Date | Mon, 10 Oct 2005 14:39:32 -0700 |
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On Mon, 2005-10-10 at 14:12 -0700, Mark Knecht wrote: > On 10/10/05, Daniel Walker <dwalker@mvista.com> wrote: > > On Mon, 2005-10-10 at 13:16 -0700, Mark Knecht wrote: > > > Hi, > > > > > > > > How can I get data that would be more useful in terms of real debug? > > > > The IRQ off times look like the worst . If you do "make menuconfig" > > > > then goto Kernel Hacking and select > > "Interrupts-off critical section latency timing" > > Then select "Latency tracing" > > > > Then when you boot the system before run the following, > > > > "echo 0 > /proc/sys/kernel/preempt_max_latency" > > So this disables the tracing of preempt times but keeps IRQ times on? Cool.
Yes, that what the compile options are doing.
> > > > That will record a trace for every maximum latency observed for IRQ > > latency . You can view the trace with this command > > "cat /proc/latency_trace" , and you can attach the trace to an email to > > LKML so we can review it (compress it if it's big though) . > > > > Daniel > > Will do. Building now. I'll be back later. > > Is there anything specific I should look for in the traces myself? > Anyway to help narrow it down?
You want the trace to represent the largest latency. For instance in the histogram it showed IRQ latency was ~3000us or greater, so you want the trace to show at least that size latency .
Daniel
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