Re: Latency data - 2.6.14-rc3-rt13

From: Daniel Walker (dwalker_at_mvista.com)
Date: 10/10/05

  • Next message: Mikulas Patocka: "Re: [PATCH] Use of getblk differs between locations" 
    To: Mark Knecht <markknecht@gmail.com>
Date:	Mon, 10 Oct 2005 14:44:33 -0700

    On Mon, 2005-10-10 at 14:28 -0700, Mark Knecht wrote:
    > On 10/10/05, Mark Knecht <markknecht@gmail.com> wrote:
    > <SNIP>
    > > > then goto Kernel Hacking and select
    > > > "Interrupts-off critical section latency timing"
    > > > Then select "Latency tracing"
    >
    > Only had to turn on Latency Tracing. The others I had on...
    >
    > <SNIP>
    > > >
    > > > Daniel
    > >
    > > Will do. Building now. I'll be back later.
    > >
    >
    > Unfortunately I didn't think I'd be back this fast. I built the new
    > kernel and rebooted. The boot starts, gets down to the point where it
    > tells me that the preempt debug stuff is on, and then jumps to an
    > endlessly repeating error message:
    >
    > init[1]: segfault at ffffffff8010fce0 rip ffffffff8010fce0 rsp
    > 00007fffffcb09b8 error 15
    >
    > This error repeasts endlessly until I reboot.
    >
    > Good thing I had another kernel I could boot back into! ;-)
    >
    > So, something isn't happy. Is this a -rt thing or a kernel issue?

    Hmm, it looks like latency tracing doesn't work on x86_64 .. I guess
    you'll have to wait till someone fixes it .

    Another option is to turn off "Latency Tracing" then reboot, like it was
    before but w/o the histogram. Then run,

    "echo 0 > /proc/sys/kernel/preempt_max_latency"

    Whenever a new maximum latency is observed it will log it with a stack
    trace in the system logs. You can report that back here on LKML .

    You can view the system log with the command "dmesg" , I think .

    Daniel

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  • Next message: Mikulas Patocka: "Re: [PATCH] Use of getblk differs between locations"

    Relevant Pages

    • Re: RT patch breaks X86_64 build
      ... Syscalls are numbered from zero, ... Patch attached. ... Nonetheless the latency tracing still doesn't work for me on x86_64. ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    • Re: Latency data - 2.6.14-rc3-rt13
      ... >> the timer that you set in the kernel hacking section. ... let me take that back - latency tracing does work on x64 too. ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)