Re: [RFC][PATCH 00/17 v2] tracing: Use TRACE_DEFINE_ENUM() to show enum values

Masami Hiramatsu
2015-04-07T00:45:08Z

(2015/04/02 10:56), Steven Rostedt wrote:
> As there are many tracepoints that use __print_symbolic() to translate
> numbers into ASCII strings, and several of these translate enums as
> well, it causes a problem for user space tools that read the tracepoint
> format files and have to translate the binary data to their associated
> strings.
>
> For example, with the tlb_flush tracepoint, we have this in the format
> file:
>
> print fmt: "pages:%ld reason:%s (%d)", REC->pages,
> __print_symbolic(REC->reason,
> { TLB_FLUSH_ON_TASK_SWITCH, "flush on task switch" },
> { TLB_REMOTE_SHOOTDOWN, "remote shootdown" },
> { TLB_LOCAL_SHOOTDOWN, "local shootdown" },
> { TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" }), REC->reason
>
> Now, userspace does not know what the value of TLB_REMOTE_SHOOTDOWN is.
> To solve this, a new macro is created as a helper to allow tracepoints
> to export enums they use to userspace. This macro is called,
> TRACE_DEFINE_ENUM(), such that
>
> TRACE_DEFINE_ENUM(TLB_REMOTE_SHOOTDOWN);
>
> will convert the "print fmt"s in the format files to its actual value
> and no longer display the enum name.
>
> On boot up (or module load), the enums saved via TRACE_DEFINE_ENUM()
> will be searched for in the TP_printk()s of the tracepoints. Logic
> knows enough to ignore quoted text.
>
> For debugging, a new file is still added in the tracing directory
> to show what enums were added, their values and the TRACE_SYSTEM that
> added them:
>
> # cat /sys/kernel/debug/tracing/enum_map
> TLB_LOCAL_MM_SHOOTDOWN 3 (tlb)
> TLB_LOCAL_SHOOTDOWN 2 (tlb)
> TLB_REMOTE_SHOOTDOWN 1 (tlb)
> TLB_FLUSH_ON_TASK_SWITCH 0 (tlb)
>
> And the output of the tlb_flush format is now:
>
> print fmt: "pages:%ld reason:%s (%d)", REC->pages,
> __print_symbolic(REC->reason,
> { 0, "flush on task switch" },
> { 1, "remote shootdown" },
> { 2, "local shootdown" },
> { 3, "local mm shootdown" }), REC->reason
>
> And userspace tools can easily parse that without special handling.

Great! :)
Thank you for updating the series :D
Now I'm OK for this series.

>
> Local SHA1: a6862181206543b6493c73690f322868c86de0ea
>
>
> Steven Rostedt (Red Hat) (17):
> tracing: Add TRACE_SYSTEM_VAR to intel-sst
> tracing: Add TRACE_SYSTEM_VAR to kvm-s390
> tracing: Add TRACE_SYSTEM_VAR to xhci-hcd
> tracing: Give system name a pointer
> tracing: Update trace-event-sample with TRACE_SYSTEM_VAR documentation
> tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values
> tracing: Allow for modules to export their trace enums as well
> tracing/samples: Update the trace-event-sample.h with TRACE_DEFINE_ENUM()
> tracing: Show the mapped enums in enum_map file
> x86/tlb/trace: Export enums in used by tlb_flush tracepoint
> net/9p/tracing: Export enums in tracepoints to userspace
> f2fs: Export the enums in the tracepoints to userspace
> irq/tracing: Export enums in tracepoints to user space
> mm: tracing: Export enums in tracepoints to user space
> SUNRPC: Export enums in tracepoints to user space
> v4l: Export enums used by tracepoints to user space
> writeback: Export enums used by tracepoint to user space
>
> ----
> arch/s390/kvm/trace-s390.h | 7 +
> drivers/usb/host/xhci-trace.h | 7 +
> include/asm-generic/vmlinux.lds.h | 5 +-
> include/linux/ftrace_event.h | 4 +-
> include/linux/module.h | 2 +
> include/linux/tracepoint.h | 8 +
> include/trace/events/9p.h | 157 ++++++++--------
> include/trace/events/f2fs.h | 30 ++++
> include/trace/events/intel-sst.h | 7 +
> include/trace/events/irq.h | 39 ++--
> include/trace/events/migrate.h | 42 +++--
> include/trace/events/sunrpc.h | 62 +++++--
> include/trace/events/tlb.h | 30 +++-
> include/trace/events/v4l2.h | 75 +++++---
> include/trace/events/writeback.h | 33 +++-
> include/trace/ftrace.h | 41 ++++-
> kernel/module.c | 3 +
> kernel/trace/trace.c | 276 ++++++++++++++++++++++++++++-
> kernel/trace/trace.h | 2 +
> kernel/trace/trace_events.c | 98 +++++++++-
> samples/trace_events/trace-events-sample.h | 84 ++++++++-
> 21 files changed, 853 insertions(+), 159 deletions(-)
>
>

--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com