|| ||Ingo Molnar <mingo-AT-elte.hu>|
|| ||Jason Baron <jbaron-AT-redhat.com>|
|| ||Re: [PATCH 0/3] tracing/ftrace: ftrace_bprintk|
|| ||Tue, 24 Feb 2009 18:25:30 +0100|
|| ||Frederic Weisbecker <fweisbec-AT-gmail.com>,
linux-kernel-AT-vger.kernel.org, Steven Rostedt <rostedt-AT-goodmis.org>,
Lai Jiangshan <laijs-AT-cn.fujitsu.com>,
Peter Zijlstra <peterz-AT-infradead.org>,
Arnaldo Carvalho de Melo <acme-AT-redhat.com>|
|| ||Article, Thread
* Jason Baron <firstname.lastname@example.org> wrote:
> On Tue, Feb 24, 2009 at 06:16:18AM +0100, Frederic Weisbecker wrote:
> > Hi,
> > These three patches are part of a patchset posted by Lai Jiangshan in december 2008.
> > They introduce a binary version of ftrace_printk() called ftrace_bprintk()
> > While having the same goal: print a generic message entry into the ring buffer,
> > their approaches are very different.
> > - ftrace_printk() does the formatting job on tracing time, insert the whole resulting string
> > into the ring buffer, and then the string is printed on output time without a lot of
> > - ftrace_bprintk() does no formatting on tracing time. Instead, it looks at the format string
> > to find the types and the numbers of the arguments and directly stores them as-is into the
> > ring-buffer. Then the format string is stored into the ring-buffer too, but only by its
> > it is not copied. Then on output time only, the final string is formatted and sent to the
> > This gives a result about as fast as a traditional tracer with fixed fields types, except
> > we can print random types and numbers of fields here.
> > The first patch adds the generic support for binary formatting.
> > The second adds the support for binary print types on ftrace
> > and the last introduces ftrace_bprintk() which supports safely the modules
> > by listening on the module loading/unloading notifier to keep track of
> > unwanted freed format strings.
> > Lai Jiangshan (3):
> > add binary printf
> > ftrace: infrastructure for supporting binary record
> > ftrace: add ftrace_bprintk()
> this seems like a really valuable feature....I'm just
> wondering about a couple of things....
> If the 'brpintk tracer' in trace/trace_bprintk.c is just being
> used to set an enabled flag for printing out these binary
> records, then are we better off with just an option flag in
> the 'trace_options' file?
> Second, can we somehow combine ftrace_printk() and
> ftrace_bprintk(), so that a developer can just use one
> interface? Perhaps, ftrace_printk calls ftrace_bprintk if
> binary option flag is set, otherwise, it just outputs things
Well, ftrace_bprintk() seems to be a worthy and transparent
replacement for ftrace_printk() to me. I.e. lets just use this
as the new implementation for ftrace_printk().
Would there be any downsides of doing so? I dont see any.
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