linux-kernel - Re: [PATCH v0 23/71] perf evlist: Add perf_evlist__to

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Date:	Wed, 11 Dec 2013 16:38:40 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH v0 23/71] perf evlist: Add perf_evlist__to_front()

Em Wed, Dec 11, 2013 at 02:36:35PM +0200, Alexander Shishkin escreveu:
> From: Adrian Hunter <adrian.hunter@...el.com>
 
> Add a function to move a selected event to the front of the list.
 
> This is needed because it is not possible to use the
> PERF_EVENT_IOC_SET_OUTPUT IOCTL from an Instruction Tracing event to a
> non-Instruction Tracing event.  Thus the Instruction Tracing event
> must come first.


The description doesn't matches what the code is doing, as it is moving
a _group_, not an event.

Also I wonder if you can't do this more effiently by finding where it
starts, ends and then doing some more splice like operatins instead of
moving member by member to a temp list. Setting the (next, prev) fields
of the various sublists to the right places.

There is even list_cut_position() already in list.h, used with
list_move() and list_splice() I think you can do it more efficiently,
I think.

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/util/evlist.c | 17 +++++++++++++++++
>  tools/perf/util/evlist.h |  3 +++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index f9dbf5f..93683bc 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1216,3 +1216,20 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
>  
>  	return 0;
>  }
> +
> +void perf_evlist__to_front(struct perf_evlist *evlist,
> +			   struct perf_evsel *move_evsel)
> +{
> +	struct perf_evsel *evsel, *n;
> +	LIST_HEAD(move);
> +
> +	if (move_evsel == perf_evlist__first(evlist))
> +		return;
> +
> +	list_for_each_entry_safe(evsel, n, &evlist->entries, node) {
> +		if (evsel->leader == move_evsel->leader)
> +			list_move_tail(&evsel->node, &move);
> +	}
> +
> +	list_splice(&move, &evlist->entries);
> +}
> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> index 8a04aae..9f64ede 100644
> --- a/tools/perf/util/evlist.h
> +++ b/tools/perf/util/evlist.h
> @@ -194,5 +194,8 @@ static inline void perf_mmap__write_tail(struct perf_mmap *md,
>  }
>  
>  bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str);
> +void perf_evlist__to_front(struct perf_evlist *evlist,
> +			   struct perf_evsel *move_evsel);
> +
>  
>  #endif /* __PERF_EVLIST_H */
> -- 
> 1.8.5.1
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