linux-kernel - Re: [PATCH V5 05/12] perf/x86/intel: Support adaptive PEBSv4

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Date:   Mon, 8 Apr 2019 16:55:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V5 05/12] perf/x86/intel: Support adaptive PEBSv4

On Tue, Apr 02, 2019 at 12:45:02PM -0700, kan.liang@...ux.intel.com wrote:
> +static u64 pebs_update_adaptive_cfg(struct perf_event *event)
> +{
> +	struct perf_event_attr *attr = &event->attr;
> +	u64 sample_type = attr->sample_type;
> +	u64 pebs_data_cfg = 0;
> +	bool gprs, tsx_weight;
> +
> +	if ((sample_type & ~(PERF_SAMPLE_IP|PERF_SAMPLE_TIME)) ||
> +	    attr->precise_ip < 2) {
> +
> +		if (sample_type & PERF_PEBS_MEMINFO_TYPE)
> +			pebs_data_cfg |= PEBS_DATACFG_MEMINFO;
> +
> +		/*
> +		 * Cases we need the registers:
> +		 * + user requested registers
> +		 * + precise_ip < 2 for the non event IP
> +		 * + For RTM TSX weight we need GPRs too for the abort
> +		 * code. But we don't want to force GPRs for all other
> +		 * weights.  So add it only collectfor the RTM abort event.
> +		 */
> +		gprs = (sample_type & PERF_SAMPLE_REGS_INTR) &&
> +			      (attr->sample_regs_intr & 0xffffffff);

did that want to be:

			(attr->sample_regs_intr & PEBS_GPRS_REGS);
?

> +		tsx_weight = (sample_type & PERF_SAMPLE_WEIGHT) &&
> +			     ((attr->config & 0xffff) == x86_pmu.force_gpr_event);

Why does that force_gpr_event exist? and why isn't it called
rtm_abort_event?

Also did that want to be:

			(attr->config & INTEL_ARCH_EVENT_MASK)
?

> +		if (gprs || (attr->precise_ip < 2) || tsx_weight)
> +			pebs_data_cfg |= PEBS_DATACFG_GPRS;
> +
> +		if ((sample_type & PERF_SAMPLE_REGS_INTR) &&
> +		    (attr->sample_regs_intr >> 32))

Surely, you meant:

		(attr->sample_regs_intr & PEBS_XMM_REGS)
?

> +			pebs_data_cfg |= PEBS_DATACFG_XMMS;
> +
> +		if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
> +			/*
> +			 * For now always log all LBRs. Could configure this
> +			 * later.
> +			 */
> +			pebs_data_cfg |= PEBS_DATACFG_LBRS |
> +				((x86_pmu.lbr_nr-1) << PEBS_DATACFG_LBR_SHIFT);
> +		}
> +	}
> +	return pebs_data_cfg;
> +}