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

[Masami Hiramatsu]

(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@xxxxxxxxxxx


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