linux-kernel - Re: using SDT events

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Date:   Tue, 27 Sep 2016 11:40:26 -0700
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     wang@...radead.org, Jiri Olsa <jolsa@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: using SDT events

On Tue, 27 Sep 2016 10:55:38 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Masami,
> 
> 	Testing something else (event aliases/JSON) I saw the many sdt
> events available via 'perf list', decided to use the usual workflow,
> failed, what am I doing wrong?

No, that is not supported yet. So I dropped perf-list support from
the latest series...

https://lkml.org/lkml/2016/7/1/133

The unresolved problems are 
 - how we treat sdt events after recorded? remove or leave it as tracepoint?
 - what should be done if we found the tracepoint which has same name of the
   SDT. (we can not reserve tracepoint name beforehand)
 - Sometimes SDT name can be conflict, even on same binary.


> 
> 
> [root@...et ~]# perf list sdt_qemu:pci*
> 
> List of pre-defined events (to be used in -e):
> 
>   sdt_qemu:pci_cfg_read                              [SDT event]
>   sdt_qemu:pci_cfg_write                             [SDT event]
>   sdt_qemu:pci_update_mappings_add                   [SDT event]
>   sdt_qemu:pci_update_mappings_del                   [SDT event]
> [root@...et ~]# perf record -e sdt_qemu:pci* -a
> event syntax error: 'sdt_qemu:pci*'
>                      \___ unknown tracepoint
> 
> Error:	File /sys/kernel/debug/tracing/events/sdt_qemu/pci* not found.
> Hint:	Perhaps this kernel misses some CONFIG_ setting to enable this
> feature?.
> 
> Run 'perf list' for a list of valid events
> 
>  Usage: perf record [<options>] [<command>]
>     or: perf record [<options>] -- <command> [<options>]
> 
>     -e, --event <event>   event selector. use 'perf list' to list
> available events
> [root@...et ~]# 


-- 
Masami Hiramatsu <mhiramat@...nel.org>