Date: Sun, 5 Jul 2015 16:32:02 -0700 From: Mark Johnston <markj@FreeBSD.org> To: Ryan Stone <rysto32@gmail.com> Cc: abhishek kulkarni <abhya007@gmail.com>, Ryan Stone <rstone@freebsd.org>, "freebsd-dtrace@freebsd.org" <freebsd-dtrace@freebsd.org> Subject: Re: Regarding schedgraph.d Message-ID: <20150705233202.GA70385@raichu> In-Reply-To: <CAFMmRNy0AFBazEKR=QFY1h6htTre=Zi=dd==2c7Dkfc7BygZ%2BQ@mail.gmail.com> References: <CAJUVsesOHQegeS=yfED8iKUoJK5KEVnLBqKH1MpSUuH_4i=_RQ@mail.gmail.com> <CAFMmRNwu8SoX-dJPb1wBh26UnXAnM5x7FZprDmXpVXbS7htkYQ@mail.gmail.com> <CAJUVseuHN-hLvLP6AQZdjwnQqpB24nSfm-dAWmn=j3y1EYiEMw@mail.gmail.com> <CAFMmRNy0AFBazEKR=QFY1h6htTre=Zi=dd==2c7Dkfc7BygZ%2BQ@mail.gmail.com>
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On Thu, Jul 02, 2015 at 07:40:21PM -0400, Ryan Stone wrote: > The best that I can offer right now is the Illumos documentation: > > http://dtrace.org/guide/chp-sched.html I wrote and committed some DTrace provider man pages a little while ago. The page for the sched provider is here: https://www.freebsd.org/cgi/man.cgi?query=dtrace-sched&sektion=4&apropos=0&manpath=FreeBSD+11-current > > The caveat is that the types documented there are not implemented in > FreeBSD. Where illumos uses a lwpsinfo_t, FreeBSD uses a struct thread: > > https://svnweb.freebsd.org/base/head/sys/sys/proc.h?revision=284215&view=markup#l206 > > psinfo_t is replaced by struct proc. > > https://svnweb.freebsd.org/base/head/sys/sys/proc.h?revision=284215&view=markup#l495 > > cpuinfo_t* arguments are not implemented and passed as NULL. You can > access the current cpu number using the "cpu" variable. > > > Finally, the schedctl-* probes don't apply to the FreeBSD scheduler and > therefore are unimplemented. I removed them in r281702: our sched provider uses FreeBSD types and thus is already incompatible with the Solaris/illumos sched provider, so it didn't make much sense to me to keep them around. > > > On Thu, Jul 2, 2015 at 12:30 PM, abhishek kulkarni <abhya007@gmail.com> > wrote: > > > Thanks Ryan. Those are some very useful tips. Ill get on with trying all > > of those and get back If I have some more concerns. Also, could you be > > having some document which has some logical description about the "sched" > > probes for FreeBSD, which could give details like when is the particular > > probe fired, the probe's arguments etc. Thanks again. > > > > Regards > > Abhishek Kulkarni > > > > On Wed, Jul 1, 2015 at 1:51 PM, Ryan Stone <rysto32@gmail.com> wrote: > > > >> On Tue, Jun 30, 2015 at 7:11 PM, abhishek kulkarni <abhya007@gmail.com> > >> wrote: > >> > >>> Hello Ryan, > >>> > >>> I was looking to schedgraph.d . I need to modify the script for a > >>> single, particular thread. I atleast need to know the thread transitions, > >>> as in the context switches for the particular thread and also the different > >>> states for a single thread. Could you please help with the filters that I > >>> need to add in order to use the script for a single thread or else suggest > >>> me just the nexessary probes that I could use for writing a new script for > >>> a single thread . > >>> > >>> Regards > >>> Abhishek Kulkarni > >>> > >> > >> There are a couple of things that you could filter on, depending on what > >> you know about the thread of interest. The "execname" variable gives the > >> name of the current process. If you're interesting in tracing a > >> single-threaded process, that would be an option. Another variable of > >> interest would be the "curthread" variable. This gives a pointer to the > >> "struct thread" for the current thread. One field that you could trace on > >> would be curthread->td_tid. You can use ps to find your thread id and then > >> run the script as: > >> > >> dtrace -s script.d <tid> > >> > >> And in the script, filter with / curthread->td_tid == $1 /. Another > >> field that you could use would be curthread->td_name, which contains the > >> name of the current thread. If your application names threads with > >> "pthreads_set_name_np()", then that name will appear in td_name and you can > >> filter based off of that. > >> > >> An alternative approach would be to use a thread-local variable. If you > >> know that your thread is the only thread that might hit a probe, you can > >> set a thread local variable in that probe and filter on it later on. For > >> example, if your thread is the only thread that will call a function called > >> foobar() in the kernel, you could do this: > >> > >> fbt::foobar:entry > >> { > >> self->interesting = 1; > >> } > >> > >> sched:::off-cpu > >> / self->interesting / > >> { > >> /* trace interesting data here */ > >> } > >> > >> > > > _______________________________________________ > freebsd-dtrace@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-dtrace > To unsubscribe, send any mail to "freebsd-dtrace-unsubscribe@freebsd.org"
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