linux-kernel - Re: [PATCH v2 3/8] drivers/perf: hisi_pcie: Fix incorrect counting under metric mode

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Date: Mon, 26 Feb 2024 15:12:30 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Yicong Yang <yangyicong@...wei.com>
CC: <will@...nel.org>, <mark.rutland@....com>, <hejunhao3@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<yangyicong@...ilicon.com>, <linuxarm@...wei.com>,
	<prime.zeng@...ilicon.com>, <fanghao11@...wei.com>
Subject: Re: [PATCH v2 3/8] drivers/perf: hisi_pcie: Fix incorrect counting
 under metric mode

On Fri, 23 Feb 2024 18:33:54 +0800
Yicong Yang <yangyicong@...wei.com> wrote:

> From: Yicong Yang <yangyicong@...ilicon.com>
> 
> The metric counting shows incorrect results if the events in the
> metric group using the same event but different filter options.
> This is because we only judge the event code to decide whether
> the event in the metric group should share the same hardware
> counter, but ignore the settings of the filter.
> 
> For example, on a platform of 2 ports 0x1 and 0x2 but only port
> 0x1 has a downstream PCIe NVME device. The metric counting
> shows both ports have the same counts because we misassign these
> two events to one same hardware counter:
> [root@...alhost perf-iostat]# ./perf stat -e '{hisi_pcie0_core1/event=0x0104,port=0x2/,hisi_pcie0_core1/event=0x0104,port=0x1/}'
> 
>  Performance counter stats for 'system wide':
> 
>         7907484924      hisi_pcie0_core1/event=0x0104,port=0x2/
>         7907484924      hisi_pcie0_core1/event=0x0104,port=0x1/
> 
>       10.153863691 seconds time elapsed
> 
> Fix this by using the whole config rather than the event only
> to judge whether two events are the same and should share the
> same hardware counter. With this patch, the metric counting in
> the above case tends to be corrected:
> 
> [root@...alhost perf-iostat]# ./perf stat -e '{hisi_pcie0_core1/event=0x0104,port=0x2/,hisi_pcie0_core1/event=0x0104,port=0x1/}'
> 
>  Performance counter stats for 'system wide':
> 
>                  0      hisi_pcie0_core1/event=0x0104,port=0x2/
>         8123122077      hisi_pcie0_core1/event=0x0104,port=0x1/
> 
>       10.152875631 seconds time elapsed
> 
> Fixes: 8404b0fbc7fb ("drivers/perf: hisi: Add driver for HiSilicon PCIe PMU")
> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>