Re: [Qemu-devel] [PATCH] tcg: add ability to dump /tmp/perf-<pid>.map files

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson writes:

> On 07/11/2014 09:43 AM, Alex Bennée wrote:
>> +/* if I could put this in a header easily.... */
>> +void tb_enable_perfmap(void);
>
> How about next to tb_flush in exec/exec-all.h?

Including exec/exec-all.h trips up some sort of include prevention
magic:

  CC    vl.o
In file included from vl.c:82:0:
/home/alex/lsrc/qemu/qemu.git/include/exec/exec-all.h:75:28: error: attempt to use poisoned "CPUArchState"
 void gen_intermediate_code(CPUArchState *env, struct TranslationBlock *tb);
                            ^
>> +
>> +void tb_enable_perfmap(void) {
>
> Watch the { placement.
>
>> +    gchar * map_file = g_strdup_printf("/tmp/perf-%d.map", getpid());
>> +    tb_perfmap = fopen(map_file, "w");
>> +    g_free(map_file);
>> +}
>
> And speaking of tb_flush, ought there be some marker in the perf file to reset
> things?  Otherwise you're just going to wind up with garbage if you let the
> guest run long enough.
>
> Of course, I have no idea how to link the flush with a timestamp that allows
> one to selectively choose which section of the perf file one uses...

The perf JIT format isn't really that smart so currently I'm not sure
how it would deal with it. Currently I suspect the best solution is
"don't do that then" :-/

>
>
> r~

-- 
Alex Bennée