linux-kernel - Re: [PATCH v5 12/20] x86: perf: intel

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Message-ID: <20141022152644.GZ12706@worktop.programming.kicks-ass.net>
Date:	Wed, 22 Oct 2014 17:26:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	adrian.hunter@...el.com, acme@...radead.org
Subject: Re: [PATCH v5 12/20] x86: perf: intel_pt: Intel PT PMU driver

On Mon, Oct 13, 2014 at 04:45:40PM +0300, Alexander Shishkin wrote:
> +static void pt_event_start(struct perf_event *event, int mode)
> +{
> +	struct pt *pt = this_cpu_ptr(&pt_ctx);
> +	struct pt_buffer *buf = perf_get_aux(&pt->handle);
> +
> +	if (pt_is_running() || !buf || pt_buffer_is_full(buf, pt) ||
> +	    pt_config(event)) {
> +		event->hw.state = PERF_HES_STOPPED;
> +		return;
> +	}
> +
> +	ACCESS_ONCE(pt->handle_nmi) = 1;
> +	event->hw.state = 0;
> +
> +	pt_config_buffer(buf->cur->table, buf->cur_idx,
> +			 buf->output_off);
> +	wrmsrl(MSR_IA32_RTIT_STATUS, 0);
> +	pt_config_start(true);
> +}

That's two RTIT_CTL writes, should we not try and merge those?
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