linux-kernel - Re: [PATCH v7 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe PMU

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Message-ID: <95de93f7-1618-5aa6-9a23-6445c5cb3515@huawei.com>
Date:   Sat, 26 Jun 2021 10:13:00 +0800
From:   "liuqi (BA)" <liuqi115@...wei.com>
To:     John Garry <john.garry@...wei.com>, Linuxarm <linuxarm@...wei.com>,
        <will@...nel.org>, <mark.rutland@....com>, <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <zhangshaokun@...ilicon.com>
Subject: Re: [PATCH v7 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe
 PMU



On 2021/6/25 23:53, John Garry wrote:
> On 24/06/2021 11:59, Qi Liu wrote:
>> +
>> +/*
>> + * Events with the "dl" suffix in their names count performance in DL 
>> layer,
>> + * otherswise, events count performance in TL layer.
>> + */
>> +static struct attribute *hisi_pcie_pmu_events_attr[] = {
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_rx_mwr, 0x010004),
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_rx_mrd, 0x100005),
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_tx_mwr, 0x010005),
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_tx_mrd, 0x200004),
>> +    HISI_PCIE_PMU_EVENT_ATTR(lat_rx_mwr, 0x000010),
>> +    HISI_PCIE_PMU_EVENT_ATTR(lat_rx_mrd, 0x020010),
>> +    HISI_PCIE_PMU_EVENT_ATTR(lat_tx_mrd, 0x000011),
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_rx_dl, 0x010084),
>> +    HISI_PCIE_PMU_EVENT_ATTR(bw_tx_dl, 0x030084),
>> +    NULL
>> +};
>> +
>> +static struct attribute_group hisi_pcie_pmu_events_group = {
>> +    .name = "events",
>> +    .attrs = hisi_pcie_pmu_events_attr,
>> +};
>> +
>> +static struct attribute *hisi_pcie_pmu_format_attr[] = {
>> +    HISI_PCIE_PMU_FORMAT_ATTR(event, "config:0-15"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(subevent, "config:16-23"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(thr_len, "config1:0-3"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(thr_mode, "config1:4"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(trig_len, "config1:5-8"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(trig_mode, "config1:9"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(port, "config2:0-15"),
>> +    HISI_PCIE_PMU_FORMAT_ATTR(bdf, "config2:16-31"),
>> +    NULL
>> +};
> 
> I am just wondering how this now works.
> 
> So if the user programs the following:
> ./perf stat -v -e hisi_pcieX/lat_rx_mrd/
> 
> Then the value (incremented) in HISI_PCIE_CNT (I think that's the right 
> one) is returned as the event count. But one would expect bandwidth from 
> that event, while we only return here the delay cycles - how is the 
> count in HISI_PCIE_CNT_EXT exposed, so userspace can do the calc for bw?
> 

Hi John,

Hardware counter and ext_counter work together for bandwidth, latency,
bus utilization and buffer occupancy events. For example, for latency
events(idx = 0x10), counter counts total delay cycles and ext_counter
counts PCIe packets number.

As we don't want PMU driver to process these two data, "delay cycles"
can be treated as an event(id = 0x10), "packets number" as another event
(id = 0x10 << 8), and driver could export these data separately.

if the user want to calculate latency of rx memory read, they should:
./perf stat -v -e '{hisi_pcieX/event=0x10, 
subevent=0x01/,hisi_pcieX/event=0x0400, subevent=0x01/

and for bandwidth event:
./perf stat -v -e '{hisi_pcieX/event=0x4, 
subevent=0x02/,hisi_pcieX/event=0x1000, subevent=0x02/

Then the value in HISI_PCIE_CNT and HISI_PCIE_EXT_CNT returned 
separately, and userspace could do the calculation.

Thanks,
Qi
> Thanks,
> John
> .