Re: [PATCH 4/5 v3] tracing/core: drop the old ftrace_printkimplementation in favour of ftrace_bprintk

From: Ingo Molnar
Date: Fri Mar 06 2009 - 12:14:37 EST



* Ingo Molnar <mingo@xxxxxxx> wrote:

>
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> >
> >
> > On Fri, 6 Mar 2009, Frederic Weisbecker wrote:
> >
> > > Impact: faster and lighter tracing
> > >
> > > Now that we have ftrace_bprintk() which is faster and consume lesser
> > > memory than ftrace_printk() and has the same purpose, we can now drop
> > > the old implementation in favour of the binary one from ftrace_bprintk(),
> > > which means we move all the implementation of ftrace_bprintk() to
> > > ftrace_printk(), so the Api doesn't change except that we must now use
> > > trace_seq_bprintk() to print the TRACE_PRINT entries.
> > >
> > > Some changes result of this:
> > >
> > > - Previously, ftrace_bprintk depended of a single tracer and couldn't
> > > work without. This tracer has been dropped and the whole implementation
> > > of ftrace_printk() (like the module formats management) is now integrated
> > > in the tracing core (comes with CONFIG_TRACING), though we keep the file
> > > trace_printk (previously trace_bprintk.c) where we can find the module
> > > management. Thus we don't overflow trace.c
> > >
> > > - changes some parts to use trace_seq_bprintk() to print TRACE_PRINT entries.
> > >
> > > - change a bit ftrace_printk/ftrace_vprintk macros to support non-builtin formats
> > > constants, and fix 'const' qualifiers warnings. But this is all transparent for
> > > developers.
> > >
> > > - etc...
> > >
> > > V2:
> > >
> > > - Rebase against last changes
> > > - Fix mispell on the changelog
> > >
> > > V3:
> > >
> > > - Rebase against last changes (moving ftrace_printk() to kernel.h)
> > >
> > > Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> >
> > Very nice Frederic!
> >
> > For some reason I'm still missing patch 1. Perhaps it decided to take the
> > scenic route ;-)
> >
> > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > > index 0f5077f..6140922 100644
> > > --- a/kernel/trace/trace.h
> > > +++ b/kernel/trace/trace.h
> > > @@ -20,7 +20,6 @@ enum trace_type {
> > > TRACE_WAKE,
> > > TRACE_STACK,
> > > TRACE_PRINT,
> > > - TRACE_BPRINTK,
> > > TRACE_SPECIAL,
> > > TRACE_MMIO_RW,
> > > TRACE_MMIO_MAP,
> > > @@ -120,16 +119,10 @@ struct userstack_entry {
> > > */
> > > struct print_entry {
> > > struct trace_entry ent;
> > > - unsigned long ip;
> > > + unsigned long ip;
> > > int depth;
> > > - char buf[];
> > > -};
> > > -
> >
> >
> > Note, this is going to break my recent patch that exports the
> > internal ftrace events. That's OK, I'll fix it after Ingo
> > pulls it in.
> >
> > Ingo,
> >
> > Would you prefer that I pull these patches in and then fix the
> > code, and let you pull it from me?
>
> i've put them into a separate branch forked off
> tip:tracing/ftrace: tip:tracing/printk. The two vsprintf
> patches are in tip:core/printk and merged into tracing/ftrace.
>
> You can thus apply your current enhancements without any
> interaction with me - and merge tracing/printk into the
> tip:tracing/ftrace branch on your own schedule, ok?

ah - i misunderstood - i see that it interacts with your commits
from last night.

I've excluded tip:tracing/printk from tip:master for now and
will let you guys fix it up when you have time for it.

Ingo
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