linux-kernel - Re: [PATCH v2 13/13] perf tools: add feature header record to pipe-mode

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Message-ID: <20170525080938.GL14467@krava>
Date:   Thu, 25 May 2017 10:09:38 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     David Carrillo-Cisneros <davidcc@...gle.com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Simon Que <sque@...omium.org>,
        Wang Nan <wangnan0@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
        He Kuang <hekuang@...wei.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        David Ahern <dsa@...ulusnetworks.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH v2 13/13] perf tools: add feature header record to
 pipe-mode

On Tue, May 23, 2017 at 12:48:53AM -0700, David Carrillo-Cisneros wrote:

SNIP

> +int perf_event__process_feature(struct perf_tool *tool,
> +				union perf_event *event,
> +				struct perf_session *session __maybe_unused)
> +{
> +	struct feat_fd fd = { .fd = 0 };
> +	struct feature_event *fe = (struct feature_event *)event;
> +	int type = fe->header.type;
> +	u64 feat = fe->header_id;
> +
> +	if (type < 0 || type >= PERF_RECORD_HEADER_MAX) {
> +		pr_warning("invalid record type %d\n", type);
> +		return 0;
> +	}
> +	if (feat == HEADER_RESERVED)
> +		return -1;
> +
> +	if (feat > HEADER_LAST_FEATURE)
> +		return 0;

I think we should warn in here

> +
> +	if (!feat_ops[feat].process)
> +		return 0;
> +
> +	/*
> +	 * no print routine
> +	 */

superfluous comment

> +	if (!feat_ops[feat].print)
> +		return 0;
> +
> +	fd.buf  = (void *)fe->data;
> +	fd.size = event->header.size - sizeof(event->header);
> +	fd.ph = &session->header;
> +
> +	if (!tool->show_feat_hdr)
> +		return 0;

some of the features could provide data for processing,
should we call process unconditionaly and check this
just before calling print?

thanks,
jirka