Date: Mon, 26 Jan 2015 22:01:50 -0500 From: Ryan Stone <rysto32@gmail.com> To: Adrian Chadd <adrian@freebsd.org> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Re: Is anyone using the schedgraph.d script? Message-ID: <CAFMmRNyDRwLQEgvtyOfXsKjt_NcPYw8Nf%2BYNuFas1O=vJw2F0g@mail.gmail.com> In-Reply-To: <CAJ-VmokZ7b1Wz0CsMdbjiVBwTQW_s78ePC2USE%2ByArzrMrbXbw@mail.gmail.com> References: <CAJ-VmonoZ0bz2HRNi2s5yA7vNSeUAGjwnt80L8MBY9OOEz_9-w@mail.gmail.com> <CAJ-VmokZ7b1Wz0CsMdbjiVBwTQW_s78ePC2USE%2ByArzrMrbXbw@mail.gmail.com>
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Hm, there was one bug in that script. I uploaded a fixed version. The fix was:
- printf("%d %d KTRGRAPH group:\"thread\", id:\"%s/%s tid %d\",
state:\"runq add\", attributes: prio:%d, linkedto:\"%s/%s tid %d\"\n",
cpu, timestamp, args[0]->td_proc->p_comm, args[0]->td_name,
args[0]->td_tid, args[0]->td_priority, curthread->td_proc->p_comm,
curthread->td_name, args[0]->td_tid);
+ printf("%d %d KTRGRAPH group:\"thread\", id:\"%s/%s tid %d\",
state:\"runq add\", attributes: prio:%d, linkedto:\"%s/%s tid %d\"\n",
cpu, timestamp, args[0]->td_proc->p_comm, args[0]->td_name,
args[0]->td_tid, args[0]->td_priority, curthread->td_proc->p_comm,
curthread->td_name, curthread->td_tid);
Note that the last printf argument used args[0] instead of curthread
as intended.
One other thing that I have noticed with the schedgraph data gathering
is that unlike KTR, in dtrace every CPU gathers its data into a
CPU-local buffer. This can mean that a CPU that sees a large number
of scheduler events will roll over its ring buffer much more quickly
than a lightly loaded CPU. This can lead to a confusing or misleading
schedgraph output at the beginning of the time period. You can
mitigate this problem by allowing dtrace to allocate a larger ring
buffer with:
#pragma D option bufsize=32m
(You can potentially tune it even higher than that, but that's a good
place to start)
Finally, I've noticed that schedgraph seems to have problems
auto-detecting the clock frequency, so I tend to forcifully specify
1GHz (dtrace always outputs time in units of ns, so this is always
correct to do with dtrace-gather data)
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