linux-kernel - Re: [PATCH v3] perf/x86/intel/uncore: Fix CAS_COUNT

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Date:   Wed, 22 Dec 2021 11:30:21 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     zhengjun.xing@...ux.intel.com, peterz@...radead.org,
        mingo@...hat.com, acme@...nel.org, linux-kernel@...r.kernel.org
Cc:     adrian.hunter@...el.com, alexander.shishkin@...el.com,
        ak@...ux.intel.com, kan.liang@...el.com, stable@...r.kernel.org
Subject: Re: [PATCH v3] perf/x86/intel/uncore: Fix CAS_COUNT_WRITE issue for
 ICX



On 11/18/2021 11:02 AM, zhengjun.xing@...ux.intel.com wrote:
> From: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> 
> The user recently report a perf issue in the ICX platform, when test by

If you have the user's name, you may want to add a Reported-by tag to 
give them credit. If you don't have, it doesn't matter either.

> perf event “uncore_imc_x/cas_count_write”,the write bandwidth is always
> very small (only 0.38MB/s), it is caused by the wrong "umask" for the
> "cas_count_write" event. When double-checking, find "cas_count_read"
> also is wrong.
> 
> The public document for ICX uncore:
> 
> https://www.intel.com/content/www/us/en/develop/download/3rd-gen-intel-xeon-processor-scalable-uncore-pm.html
> 
> On page 142, Table 2-143, defines Unit Masks for CAS_COUNT:
> RD b00001111
> WR b00110000
>

I think we usually want a permanent reference in the change log. The 
document may be updated later. The page number or the table number may 
not be accurate anymore.

I guess you may want to give the exact document name and the version 
number here. So people can still easily locate the information several 
years later.
E.g., "3rd Gen Intel® Xeon® Processor Scalable Family, Codename Ice 
Lake, Uncore Performance Monitoring Reference Manual, Revision 1.00, May 
2021"


> So Corrected both "cas_count_read" and "cas_count_write" for ICX.
> 
> Old settings:
>   hswep_uncore_imc_events
> 	INTEL_UNCORE_EVENT_DESC(cas_count_read,  "event=0x04,umask=0x03")
>   	INTEL_UNCORE_EVENT_DESC(cas_count_write, "event=0x04,umask=0x0c")
> 
> New settings:
>   snr_uncore_imc_events
> 	INTEL_UNCORE_EVENT_DESC(cas_count_read,  "event=0x04,umask=0x0f")
> 	INTEL_UNCORE_EVENT_DESC(cas_count_write, "event=0x04,umask=0x30"),
> 
> Fixes: 2b3b76b5ec67 ("perf/x86/intel/uncore: Add Ice Lake server uncore support")
> Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>

Other than the above comments, the patch looks good to me.

Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>


Thanks,
Kan

> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> Cc: stable@...r.kernel.org
> ---
> Change log:
> 
>    v3:
>      * Add change log
> 
>    v2:
>      * Add stable tag
> 
>   arch/x86/events/intel/uncore_snbep.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index 5ddc0f30db6f..a6fd8eb410a9 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -5468,7 +5468,7 @@ static struct intel_uncore_type icx_uncore_imc = {
>   	.fixed_ctr_bits	= 48,
>   	.fixed_ctr	= SNR_IMC_MMIO_PMON_FIXED_CTR,
>   	.fixed_ctl	= SNR_IMC_MMIO_PMON_FIXED_CTL,
> -	.event_descs	= hswep_uncore_imc_events,
> +	.event_descs	= snr_uncore_imc_events,
>   	.perf_ctr	= SNR_IMC_MMIO_PMON_CTR0,
>   	.event_ctl	= SNR_IMC_MMIO_PMON_CTL0,
>   	.event_mask	= SNBEP_PMON_RAW_EVENT_MASK,