Re: [PATCH 00/18 v3] tracing: Use TRACE_DEFINE_ENUM() to show enum values

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

(2015/04/03 10:38), 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.
> 
> 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.
> 
> For debugging, if CONFIG_TRACE_ENUM_MAP_FILE is enabled, a file is 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)

I've reviewed all patches in this series and tested it.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

for all the patches in this series.

However, I've also found that the __print_symbolic()s in

events/scsi/scsi_dispatch_cmd_*/format
events/xfs/xfs_map_blocks_alloc/format
events/xfs/xfs_get_blocks_found/format
events/xfs/xfs_get_blocks_alloc/format
events/power/pm_qos_*/format

are not fixed yet.

Thank you,

> 
> -- Steve
> 
> Local SHA1: 6689c330e3a60defc4c89da17cf5d561649bc55b
> 
> 
> Steven Rostedt (1):
>       tracing/drm: Remove unused TRACE_SYSTEM_STRING define
> 
> 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 convert their enums to values
>       tracing/samples: Update the trace-event-sample.h with TRACE_DEFINE_ENUM()
>       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
>       tracing: Add enum_map file to show enums that have been mapped
> 
> ----
>  arch/s390/kvm/trace-s390.h                 |   7 +
>  drivers/gpu/drm/drm_trace.h                |   1 -
>  drivers/gpu/drm/i915/i915_trace.h          |   1 -
>  drivers/gpu/drm/radeon/radeon_trace.h      |   1 -
>  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/Kconfig                       |  28 +++
>  kernel/trace/trace.c                       | 304 ++++++++++++++++++++++++++++-
>  kernel/trace/trace.h                       |   2 +
>  kernel/trace/trace_events.c                | 121 +++++++++++-
>  samples/trace_events/trace-events-sample.h |  84 +++++++-
>  25 files changed, 932 insertions(+), 162 deletions(-)
> --
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> 


-- 
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