lkml.org 
[lkml]   [2009]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] tracing: adding flags to events

On Thu, 14 May 2009, Frederic Weisbecker wrote:

> On Thu, May 14, 2009 at 03:45:48PM -0400, Steven Rostedt wrote:
> >
> > Christoph has been asking about processing flags in the output. He rather
> > not see c2, and rather see what those three bits are. This patch is
> > an RFC to do just that. To test it out, I added the previous task state to
> > sched switch and used the flag processing to the printk of the
> > sched_switch event.
> >
> >
> > To add a flag, just add __print_flags to the TP_printk arguments.
> >
> > TP_STRUCT__entry(
> > __field( unsigned int, flags )
> > ),
> >
> > TP_printk("flags are %s", __print_flags(__entry->flags,
> > 0, "BIT0", 1, "BIT1", 2, "BIT2", -1))
> >
>
>
> Nice idea!
>
> Also, I wonder if that would be possible to get compounded
> bits such as GFP_KERNEL instead of __GFP_WAIT | __GFP_IO | __GFP_FS.
>
> To perform that, we could just add two fields:
>
> //__b for byte, __m for mask
>
> #define __b(b) (1 << b)
> #define __m(m) m
>
> And then you can compare using a mask.
> It also requires to clear the mask from the flags to avoid
> duplicate matches such as GFP_KERNEL | __GFP_WAIT | __GFP_IO | __GFP_FS
> and only have GFP_KERNEL, eg:
>
> const char *
> ftrace_print_flags_seq(struct trace_seq *p, unsigned long flags, ...)
> {
> const char *str;
> va_list args;
> long mask;
>
> trace_seq_init(p);
> va_start(args, flags);
> for (mask = va_arg(args, long) ; mask >= 0; mask = va_arg(args, long)) {
> str = va_arg(args, const char *);
>
> if (flags & mask != mask)
> continue;
>
> flags &= ~mask;
> if (p->len)
> trace_seq_putc(p, '|');
> trace_seq_puts(p, str);
> }
> va_end(args);
> trace_seq_putc(p, 0);
>
> return p->buffer;
> }

Nice, I'll try that. I thought about doing something similar, but I
figured to post the simplest algorithm first.


> > +#define __print_flags(flag, x...) ftrace_print_flags_seq(p, flag, x)


> > +
> > #undef TRACE_EVENT
> > #define TRACE_EVENT(call, proto, args, tstruct, assign, print) \
> > enum print_line_t \
> > @@ -127,6 +132,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
> > struct trace_seq *s = &iter->seq; \
> > struct ftrace_raw_##call *field; \
> > struct trace_entry *entry; \
> > + struct trace_seq *p; \
> > int ret; \
> > \
> > entry = iter->ent; \
> > @@ -138,7 +144,9 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
> > \
> > field = (typeof(field))entry; \
> > \
> > + p = &get_cpu_var(ftrace_event_seq); \
> > ret = trace_seq_printf(s, #call ": " print); \
> > + put_cpu(); \
>
>
>
> I don't understand the role of this per-cpu trace_seq variable.
> It doesn't seem to be used.

See it now? ;-)

-- Steve


\
 
 \ /
  Last update: 2009-05-15 01:21    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site