Re: [Qemu-devel] [PATCH] Add wildcard trace event support

["Mars.Cao" <caobingbu@gmail.com>]

On 10/20/2011 05:38 PM, Mark Wu wrote:
> A basic wildcard matching is supported in both the monitor command
> "trace-event" and the events list file. That means you can enable/disable the
> events having a common prefix in a batch. For example, virtio-blk trace events
> could be enabled using:
>      trace-event virtio_blk_* on
>
> Signed-off-by: Mark Wu<wudxw@linux.vnet.ibm.com>
> ---
>   docs/tracing.txt |    9 ++++++++-
>   trace/simple.c   |   19 +++++++++++++++++--
>   trace/stderr.c   |   17 ++++++++++++++++-
>   3 files changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/docs/tracing.txt b/docs/tracing.txt
> index 95ca16c..ea29f2c 100644
> --- a/docs/tracing.txt
> +++ b/docs/tracing.txt
> @@ -132,12 +132,19 @@ This functionality is also provided through monitor commands:
>     means disabled.
>
>   * trace-event NAME on|off
> -  Enable/disable a given trace event.
> +  Enable/disable a given trace event or a group of events having common prefix
> +  through wildcard.
>
>   The "-trace events=<file>" command line argument can be used to enable the
>   events listed in<file>  from the very beginning of the program. This file must
>   contain one event name per line.
>
> +A basic wildcard matching is supported in both the monitor command "trace
> +-event" and the events list file. That means you can enable/disable the events
> +having a common prefix in a batch. For example, virtio-blk trace events could
> +be enabled using:
> +  trace-event virtio_blk_* on
> +
>   == Trace backends ==
>
>   The "tracetool" script automates tedious trace event code generation and also
> diff --git a/trace/simple.c b/trace/simple.c
> index b639dda..869e315 100644
> --- a/trace/simple.c
> +++ b/trace/simple.c
> @@ -324,14 +324,29 @@ void trace_print_events(FILE *stream, fprintf_function stream_printf)
>   bool trace_event_set_state(const char *name, bool state)
>   {
>       unsigned int i;
> -
> +    unsigned int len;
> +    bool wildcard = false;
> +    bool matched = false;
> +
> +    len = strlen(name);
> +    if (name[len-1] == '*') {
> +        wildcard = true;
> +        len -= 1;
> +    }
>       for (i = 0; i<  NR_TRACE_EVENTS; i++) {
> +        if (wildcard) {
> +            if (!strncmp(trace_list[i].tp_name, name, len)) {
> +                trace_list[i].state = state;
> +                matched = true;
> +            }
> +            continue;
> +        }
>           if (!strcmp(trace_list[i].tp_name, name)) {
>               trace_list[i].state = state;
>               return true;
>           }
>       }
> -    return false;
> +    return matched;
>   }
>
>   /* Helper function to create a thread with signals blocked.  Use glib's
> diff --git a/trace/stderr.c b/trace/stderr.c
> index 7107c4a..6a12977 100644
> --- a/trace/stderr.c
> +++ b/trace/stderr.c
> @@ -15,14 +15,29 @@ void trace_print_events(FILE *stream, fprintf_function stream_printf)
>   bool trace_event_set_state(const char *name, bool state)
>   {
>       unsigned int i;
> +    unsigned int len;
> +    bool wildcard = false;
> +    bool matched = false;
>
> +    len = strlen(name);
> +    if (name[len-1] == '*') {
> +        wildcard = true;
> +        len -= 1;
> +    }
>       for (i = 0; i<  NR_TRACE_EVENTS; i++) {
> +        if (wildcard) {
> +            if (!strncmp(trace_list[i].tp_name, name, len)) {
> +                trace_list[i].state = state;
> +                matched = true;
> +            }
> +            continue;
> +        }
>           if (!strcmp(trace_list[i].tp_name, name)) {
>               trace_list[i].state = state;
>               return true;
>           }
>       }
> -    return false;
> +    return matched;
>   }
>
>   bool trace_backend_init(const char *events, const char *file)
I do think this idea of using wildcard (from Stefanha) is smarter than 
trace groups.
I did not find anything wrong with the code although it does not support 
events with wildcard like "virtio_*_init".

Reviewed-by: Cao,Bing Bu <mars@linux.vnet.ibm.com>
Tested-by:   Cao,Bing Bu <mars@linux.vnet.ibm.com>