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

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Date:   Thu, 18 Nov 2021 07:58:22 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     zhengjun.xing@...ux.intel.com
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        alexander.shishkin@...el.com, ak@...ux.intel.com,
        kan.liang@...el.com, stable@...r.kernel.org
Subject: Re: [PATCH] perf/x86/intel/uncore: Fix CAS_COUNT_WRITE issue for ICX

On Thu, Nov 18, 2021 at 10:48:11PM +0800, 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
> 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
> 
> 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>
> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> ---
>  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,
> -- 
> 2.25.1
> 
<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>