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Date: Tue, 07 Apr 2015 20:26:29 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Steven Rostedt <rostedt@...dmis.org>
CC: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 00/18 v3] tracing: Use TRACE_DEFINE_ENUM() to show
enum values
(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@...achi.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.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@...achi.com
--
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