Messages in this thread | | | Subject | Re: [PATCH v5 24/37] tracing: Add support for 'synthetic' events | From | Tom Zanussi <> | Date | Tue, 14 Nov 2017 13:24:56 -0600 |
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Hi Namhyung,
On Tue, 2017-11-14 at 10:21 +0900, Namhyung Kim wrote: > Hi Tom, > > On Thu, Nov 09, 2017 at 02:33:55PM -0600, Tom Zanussi wrote: > > Synthetic events are user-defined events generated from hist trigger > > variables saved from one or more other events. > > > > To define a synthetic event, the user writes a simple specification > > consisting of the name of the new event along with one or more > > variables and their type(s), to the tracing/synthetic_events file. > > > > For instance, the following creates a new event named 'wakeup_latency' > > with 3 fields: lat, pid, and prio: > > > > # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \ > > /sys/kernel/debug/tracing/synthetic_events > > > > Reading the tracing/synthetic_events file lists all the > > currently-defined synthetic events, in this case the event we defined > > above: > > > > # cat /sys/kernel/debug/tracing/synthetic_events > > wakeup_latency u64 lat; pid_t pid; int prio > > > > At this point, the synthetic event is ready to use, and a histogram > > can be defined using it: > > > > # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \ > > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger > > > > The new event is created under the tracing/events/synthetic/ directory > > and looks and behaves just like any other event: > > > > # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency > > enable filter format hist id trigger > > > > Although a histogram can be defined for it, nothing will happen until > > an action tracing that event via the trace_synth() function occurs. > > The trace_synth() function is very similar to all the other trace_* > > invocations spread throughout the kernel, except in this case the > > trace_ function and its corresponding tracepoint isn't statically > > generated but defined by the user at run-time. > > > > How this can be automatically hooked up via a hist trigger 'action' is > > discussed in a subsequent patch. > > > > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> > > --- > > [SNIP] > > +static const char *synth_field_fmt(char *type) > > +{ > > + const char *fmt = "%llu"; > > + > > + if (strcmp(type, "s64") == 0) > > + fmt = "%lld"; > > + else if (strcmp(type, "u64") == 0) > > + fmt = "%llu"; > > + else if (strcmp(type, "s32") == 0) > > + fmt = "%d"; > > + else if (strcmp(type, "u32") == 0) > > + fmt = "%u"; > > + else if (strcmp(type, "s16") == 0) > > + fmt = "%d"; > > + else if (strcmp(type, "u16") == 0) > > + fmt = "%u"; > > + else if (strcmp(type, "s8") == 0) > > + fmt = "%d"; > > + else if (strcmp(type, "u8") == 0) > > + fmt = "%u"; > > + else if (strcmp(type, "char") == 0) > > + fmt = "%d"; > > + else if (strcmp(type, "unsigned char") == 0) > > + fmt = "%u"; > > + else if (strcmp(type, "int") == 0) > > + fmt = "%d"; > > + else if (strcmp(type, "unsigned int") == 0) > > + fmt = "%u"; > > + else if (strcmp(type, "long") == 0) > > + fmt = "%ld"; > > + else if (strcmp(type, "unsigned long") == 0) > > + fmt = "%lu"; > > + else if (strcmp(type, "pid_t") == 0) > > + fmt = "%d"; > > + else if (strstr(type, "[") == 0) > > + fmt = "%s"; > > Is it for string? You may want to check it with '!='.. >
It is for a string, will change (and to strchr).
Thanks,
Tom
> Thanks, > Namhyung > > > > + > > + return fmt; > > +}
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