Re: [Qemu-devel] [Qemu-Devel][PATCH 3/3] Adding command line option to linux-user.

[Alex Bennée]

[added Markus to Cc for his view on options]

vandersonmr <address@hidden> writes:

> Added -execfreq to enable execution frequency counting and dump
> all the TB's addresses and their execution frequency at the end
> of the execution.
>
> Signed-off-by: vandersonmr <address@hidden>

This works well enough but we are going to need a way to enable this for
softmmu as well. The preference for that is to add a option group to
qemu-options.hx which will allow a number of related options to be
grouped together.

The last thing that was added was the thread=multi flag to -accel
tcg,thread=multi but unfortunately the -accel option is very much a
softmmu only option group.

Maybe it's time to add a -tcg option for all the various options so we
can have (and are likely to add)?:


  -tcg tbcount=true
  -tcg tbcount=true,tbstats=file,file=output.txt
  -tcg tbcount=true,tbstats=chardev,id=statschar

There are going to future enhancements we might consider:

  -tcg jitperf=/tmp/perf.map

A long time in the future we may even have:

  -tcg multiexitblocks=true

until it defaults to true and the knob is just there to turn it off.

The closest example of an option group shared between linux-user and
softmmu is the trace code. Both builds do a:

   qemu_add_opts(&qemu_trace_opts);

(why can't this be done by module init code?)

And then they can call the general qemu_opts parser on the top level
option:

  trace_opt_parse(arg);

So maybe we need to bite the bullet and create tcg/tcg-options.c and put
our tweaking machinery in there (and the real location of
enable_freq_count)?

Markus do you have a view?


> ---
>  linux-user/exit.c | 5 +++++
>  linux-user/main.c | 7 +++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/linux-user/exit.c b/linux-user/exit.c
> index bdda720553..0c6a2f2d5b 100644
> --- a/linux-user/exit.c
> +++ b/linux-user/exit.c
> @@ -26,8 +26,13 @@
>  extern void __gcov_dump(void);
>  #endif
>
> +extern bool enable_freq_count;
> +
>  void preexit_cleanup(CPUArchState *env, int code)
>  {
> +    if (enable_freq_count) {
> +        tb_dump_all_exec_freq();
> +    }
>  #ifdef TARGET_GPROF
>          _mcleanup();
>  #endif
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 1bf7155670..ece2d8bd8b 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -388,6 +388,11 @@ static void handle_arg_trace(const char *arg)
>      trace_file = trace_opt_parse(arg);
>  }
>
> +static void handle_arg_execfreq(const char *arg)
> +{
> +    enable_freq_count = true;
> +}
> +
>  struct qemu_argument {
>      const char *argv;
>      const char *env;
> @@ -439,6 +444,8 @@ static const struct qemu_argument arg_table[] = {
>       "",           "Seed for pseudo-random number generator"},
>      {"trace",      "QEMU_TRACE",       true,  handle_arg_trace,
>       "",           "[[enable=]<pattern>][,events=<file>][,file=<file>]"},
> +    {"execfreq",   "QEMU_EXEC_FREQ",   false,  handle_arg_execfreq,
> +     "",           "enable and dump TB's execution frequency counting"},
>      {"version",    "QEMU_VERSION",     false, handle_arg_version,
>       "",           "display version information and exit"},
>      {NULL, NULL, false, NULL, NULL, NULL}


--
Alex Bennée