linux-kernel - Re: [PATCH 1/2] perf callchain: Create an address space per thread

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Date:	Tue, 23 Sep 2014 21:49:22 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jean Pihet <jean.pihet@...aro.org>,
	Arun Sharma <asharma@...com>
Subject: Re: [PATCH 1/2] perf callchain: Create an address space per thread

Hi Jiri,

On Tue, Sep 23, 2014 at 9:24 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Tue, Sep 23, 2014 at 03:30:27PM +0900, Namhyung Kim wrote:
>> The unw_addr_space_t in libunwind represents an address space to be
>> used for stack unwinding.  It doesn't need to be create/destory
>> everytime to unwind callchain (as in get_entries) and can have a same
>> lifetime as thread (unless exec called).
>>
>> So move the address space construction/destruction logic to the thread
>> lifetime handling functions.  This is a preparation to enable caching
>> in the unwind library.
>>
>> Cc: Jiri Olsa <jolsa@...hat.com>
>> Cc: Jean Pihet <jean.pihet@...aro.org>
>> Cc: Arun Sharma <asharma@...com>
>> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> ---
>>  tools/perf/util/thread.c           |  8 ++++++++
>>  tools/perf/util/unwind-libunwind.c | 30 +++++++++++++++++++++++++-----
>>  tools/perf/util/unwind.h           | 17 +++++++++++++++++
>>  3 files changed, 50 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
>> index a9df7f2c6dc9..c1fa4a3597ea 100644
>> --- a/tools/perf/util/thread.c
>> +++ b/tools/perf/util/thread.c
>> @@ -7,6 +7,7 @@
>>  #include "util.h"
>>  #include "debug.h"
>>  #include "comm.h"
>> +#include "unwind.h"
>>
>>  int thread__init_map_groups(struct thread *thread, struct machine *machine)
>>  {
>> @@ -48,6 +49,12 @@ struct thread *thread__new(pid_t pid, pid_t tid)
>>                       goto err_thread;
>>
>>               list_add(&comm->list, &thread->comm_list);
>> +
>> +             if (unwind__prepare_access(thread) < 0) {
>
> you could call list_add below this call and thus save
> the list_del call below in error path
>
> looks like you dont need comm to be on comm_list within
> the unwind__prepare_access call

Right.  Will change.

Thanks,
Namhyung


>
>> +                     list_del(&comm->list);
>> +                     free(comm);
>> +                     goto err_thread;
>> +             }
>>       }
>
> SNIP
>
> jirka
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