Messages in this thread | | | Date | Fri, 27 Mar 2015 17:37:04 -0400 | From | Steven Rostedt <> | Subject | [RFC][PATCH 00/10] tracing: Use TRACE_DEFINE_ENUM() to show enum values |
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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 export the TLB_REMOTE_SHOOTDOWN enum to use space.
How that is done is with a new file in the debugfs tracing directory.
# cat /sys/kernel/debug/tracing/enum_map TLB_LOCAL_MM_SHOOTDOWN 3 TLB_LOCAL_SHOOTDOWN 2 TLB_REMOTE_SHOOTDOWN 1 TLB_FLUSH_ON_TASK_SWITCH 0
Now userspace, when seeing TLB_REMOTE_SHOOTDOWN in the format, knows that represents "1", and can do the conversions properly.
Local SHA1: 6115e48a506e738f0f24771b4c87e4ba90d3d1c2
Steven Rostedt (Red Hat) (10): tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values tracing: Allow for modules to export their trace enums as well 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
---- include/asm-generic/vmlinux.lds.h | 5 +- include/linux/module.h | 2 + include/linux/tracepoint.h | 7 + include/trace/events/9p.h | 157 +++++++++++++---------- include/trace/events/f2fs.h | 21 +++ 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 | 11 ++ kernel/module.c | 3 + kernel/trace/trace.c | 260 +++++++++++++++++++++++++++++++++++++- 14 files changed, 598 insertions(+), 149 deletions(-)
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