Hi Steven,
>On Mon, 2022-05-16 at 14:14 -0400, Steven Rostedt wrote:
>
>
> Are you only looking to reading some events or all of them?
I created several instances and only enabled one trace event in each
instance. I need to read all trace data from each trace_pipe in each
instance and parse the trace information in each instance's associated
thread. I found that if I read tace_pipe, then parse string, it will
not consume so much CPU resource.
>
> > this file, the handler would not be able to get trace information.
> > Becuase if I read this file, and also call tep_print_event() will
> > consume lots of CPU resoruce. how can I parse the trace event info
> > without reading this file?
>
> The tep_print_event() is easier to use, but you can do things
> manually as
> well. I'll need to write a tutorial to explain this more, but I can
> help
> you here.
>
Thanks so much for your support!!
> >
> >
> > for (i = 0; ; i++)
> > {
> > char
> > *raw_buf;
> > char
> > *cpu;
> >
> >
> > ret = asprintf(&cpu, "%s/cpu%d", per_cpu,
> > i);
> > if (ret <
> > 0)
> > pdie("Could not allocate memory for cpu
> > buffer
> > %d name", i);
> >
> >
> > ret = stat(cpu,
> > &st);
> > if (ret < 0 || !S_ISDIR(st.st_mode))
> > {
> >
> > free(cpu);
> > goto
> > start;
> >
> > }
> >
> >
> > ret = asprintf(&raw_buf, "%s/trace_pipe_raw",
> > cpu);
> > if (ret <
> > 0)
> > pdie("Could not allocate memory for cpu %d
> > raw
> > buffer name", i);
> >
> >
> > read_raw_buffer(i,
> > raw_buf);
>
> This your own code?
>
no, it is your code, from your example.
> There is a way to read it yourself and to pick and choose the evens
> you
> want.
>
> If you read the raw data, you'll need to read it in page size (found
> in the
> header tep file) tep_get_page_size(). And read one page at a time.
> Then you
> can use the kbuffer code (although I haven't finished the man pages
> for
> them)
>
> Look at the traceevent/kbuffer.h file supplied by libtraceevent.
>
> You can do something like the following:
>
> unsigned long long ts; // time stamp of event
> struct tep_record record; // should probably be allocated
>
> /* For little endian 64 bit machines */
> kbuf = kbuffer_alloc(KBUFFER_LSIZE_8, KBUFFER_ENDIAN_LITTLE);
>
> read(fd, buf, page_size);
>
> kbuffer_load_subbuffer(kbuf, buf);
>
> data = kbuffer_read_event(kbuf, &ts);
>
> if (!data)
> return; // end of sub buffer.
>
> /* Move the kbuf cursor to the next event */
> kbuffer_next_event(kbuf, NULL);
>
> /* Now data has the record */
>
> record.ts = ts;
> record.size = kbuffer_event_size(kbuf);
> record.cpu = cpu; // CPU of the trace_pipe_raw file
> record.data = data;
> record.missed_events = kbuffer_missed_events(kbuf);
>
Got it now, I should measure its CPU usage and get back to you here.
Kind regards,
Christ.
> >
|