linux-kernel - Re: [PATCH 02/17] perf auxtrace: Allow number of queues to be specified

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Message-ID: <a9b176c7-60e8-4793-a056-4ad9219fbe32@intel.com>
Date: Tue, 30 Apr 2024 09:36:48 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: James Clark <james.clark@....com>, linux-perf-users@...r.kernel.org,
 gankulkarni@...amperecomputing.com, scclevenger@...amperecomputing.com,
 coresight@...ts.linaro.org, suzuki.poulose@....com, mike.leach@...aro.org
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
 Leo Yan <leo.yan@...ux.dev>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 02/17] perf auxtrace: Allow number of queues to be
 specified

On 29/04/24 18:21, James Clark wrote:
> Currently it's only possible to initialize with the default number of
> queues and then use auxtrace_queues__add_event() to grow the array. But
> that's problematic if you don't have a real event to pass into that
> function yet.
> 
> The queues hold a void *priv member to store custom state, and for
> Coresight we want to create decoders upfront before receiving data, so
> add a new function that allows pre-allocating queues. One reason to do
> this is because we might need to store metadata (HW_ID events) that
> effects other queues, but never actually receive auxtrace data on that
> queue.
> 
> Signed-off-by: James Clark <james.clark@....com>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  tools/perf/util/auxtrace.c | 9 +++++++--
>  tools/perf/util/auxtrace.h | 1 +
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index 3684e6009b63..563b6c4fca31 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -218,15 +218,20 @@ static struct auxtrace_queue *auxtrace_alloc_queue_array(unsigned int nr_queues)
>  	return queue_array;
>  }
>  
> -int auxtrace_queues__init(struct auxtrace_queues *queues)
> +int auxtrace_queues__init_nr(struct auxtrace_queues *queues, int nr_queues)
>  {
> -	queues->nr_queues = AUXTRACE_INIT_NR_QUEUES;
> +	queues->nr_queues = nr_queues;
>  	queues->queue_array = auxtrace_alloc_queue_array(queues->nr_queues);
>  	if (!queues->queue_array)
>  		return -ENOMEM;
>  	return 0;
>  }
>  
> +int auxtrace_queues__init(struct auxtrace_queues *queues)
> +{
> +	return auxtrace_queues__init_nr(queues, AUXTRACE_INIT_NR_QUEUES);
> +}
> +
>  static int auxtrace_queues__grow(struct auxtrace_queues *queues,
>  				 unsigned int new_nr_queues)
>  {
> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> index 55702215a82d..8a6ec9565835 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -521,6 +521,7 @@ int auxtrace_mmap__read_snapshot(struct mmap *map,
>  				 struct perf_tool *tool, process_auxtrace_t fn,
>  				 size_t snapshot_size);
>  
> +int auxtrace_queues__init_nr(struct auxtrace_queues *queues, int nr_queues);
>  int auxtrace_queues__init(struct auxtrace_queues *queues);
>  int auxtrace_queues__add_event(struct auxtrace_queues *queues,
>  			       struct perf_session *session,