linux-kernel - Re: [PATCH v4 4/5] hwtracing: hisi_ptt: Advertise PERF_PMU_CAP_NO

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Message-ID: <01c39cb9-e56a-862b-2d99-024b7ba5a769@huawei.com>
Date:   Mon, 19 Jun 2023 21:00:12 +0800
From:   hejunhao <hejunhao3@...wei.com>
To:     Yicong Yang <yangyicong@...wei.com>, <mathieu.poirier@...aro.org>,
        <suzuki.poulose@....com>, <jonathan.cameron@...wei.com>,
        <corbet@....net>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>
CC:     <alexander.shishkin@...ux.intel.com>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <prime.zeng@...wei.com>,
        <yangyicong@...ilicon.com>
Subject: Re: [PATCH v4 4/5] hwtracing: hisi_ptt: Advertise
 PERF_PMU_CAP_NO_EXCLUDE for PTT PMU

Hi, Yicong


On 2023/6/6 22:22, Yicong Yang wrote:
> From: Yicong Yang <yangyicong@...ilicon.com>
>
> The PTT trace collects PCIe TLP headers from the PCIe link and don't
> have the ability to exclude certain context. It doesn't support itrace
> as well. So only advertise PERF_PMU_CAP_NO_EXCLUDE. This will greatly
> save the storage of final data. Tested tracing idle link for ~15s,
> without this patch we'll collect ~28.682MB data for context related
> information and with this patch it reduced to ~0.226MB.
>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
> ---
>   drivers/hwtracing/ptt/hisi_ptt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index 5c7e93e7705f..ff2c16efe5b1 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -1210,7 +1210,7 @@ static int hisi_ptt_register_pmu(struct hisi_ptt *hisi_ptt)
>   
>   	hisi_ptt->hisi_ptt_pmu = (struct pmu) {
>   		.module		= THIS_MODULE,
> -		.capabilities	= PERF_PMU_CAP_EXCLUSIVE | PERF_PMU_CAP_ITRACE,
> +		.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,

According to the error prompt of function hisi_ptt_trace_start().
https://elixir.bootlin.com/linux/v6.4-rc7/source/drivers/hwtracing/ptt/hisi_ptt.c#L197

You may be need to keep advertise PERF_PMU_CAP_EXCLUSIVE?
Such pmus can only have one event scheduled at a time, if not the perf
tool will report device busy.

Best regards,
Junhao.

>   		.task_ctx_nr	= perf_sw_context,
>   		.attr_groups	= hisi_ptt_pmu_groups,
>   		.event_init	= hisi_ptt_pmu_event_init,