linux-kernel - Re: [PATCH] perf tools: Allow multiple threads or processes in record, stat, top

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Date:	Fri, 10 Feb 2012 17:34:29 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	David Ahern <dsahern@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org,
	fweisbec@...il.com, paulus@...ba.org, tglx@...utronix.de
Subject: Re: [PATCH] perf tools: Allow multiple threads or processes in
 record, stat, top

Em Fri, Feb 10, 2012 at 12:32:09PM -0700, David Ahern escreveu:
> 
> 
> On 02/10/2012 12:24 PM, Arnaldo Carvalho de Melo wrote:
> > Em Wed, Feb 08, 2012 at 09:32:52AM -0700, David Ahern escreveu:
> >> Allow a user to collect events for multiple threads or processes
> >> using a comma separated list.
> >>
> >> e.g., collect data on a VM and its vhost thread:
> >>   perf top -p 21483,21485
> >>   perf stat -p 21483,21485 -ddd
> >>   perf record -p 21483,21485
> >>
> >> or monitoring vcpu threads
> >>   perf top -t 21488,21489
> >>   perf stat -t 21488,21489 -ddd
> >>   perf record -t 21488,21489
> > 
> > I found some problems below:
> >  
> >> diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
> >> index 3d4b6c5..e793c16 100644
> >> --- a/tools/perf/util/thread_map.c
> >> +++ b/tools/perf/util/thread_map.c
> >> +static struct thread_map *thread_map__new_by_pid_str(const char *pid_str)
> >> +{
> >> +	struct thread_map *threads = NULL;
> > <SNIP>
> >> +		if (threads)
> >> +			threads = realloc(threads,
> >> +					  sizeof(*threads) + sizeof(pid_t)*total_tasks);
> >> +		else
> >> +			threads = malloc(sizeof(*threads) + sizeof(pid_t)*items);
> > 
> > If realloc fails and threads was allocated before... we leak memory.
> 
> ok.
> 
> > 
> > We don't need to use this if clause, realloc handles threads == NULL
> > just fines and then works as malloc.
> 
> ok.
> 
> > 
> > Also I didn't use ctype altogether + that CSV parsing routine, we have
> > strlist for that, it even will allow us to trow away duplicate pids/tids
> > and also supports passing a file with a list of threads to monitor, for
> > free.
> 
> Interesting. I did look at strlist before going with the string parsing.
> It was not obvious to me how to use it for this case.
> 
> > 
> > Take a look at the modified patch below, if you're ok with it I can keep
> > your autorship and put a [committer note: use strlist] or take autorship
> > and state that it was based on a patch made by you, definetely your
> > call. I'd go for the committer note.
> 
> I'm fine with either one. Patch below looks fine. If needed:
> 
> Acked-by: David Ahern <dsahern@...il.com>

I assume you tested it in a few scenarios (I know I did, but hey, more
testing is always good) and that I can add another stamp, a Tested-by:
ya, right?

- Arnaldo
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