linux-kernel - Re: [PATCH 01/11] perf/amd/ibs: Throttle interrupts with filtered ldlat samples

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Message-ID: <de24ee43-fa1d-418b-855f-aef5c681a302@linux.intel.com>
Date: Mon, 19 Jan 2026 15:31:20 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Ravi Bangoria <ravi.bangoria@....com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 James Clark <james.clark@...aro.org>, x86@...nel.org,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 Manali Shukla <manali.shukla@....com>,
 Santosh Shukla <santosh.shukla@....com>,
 Ananth Narayan <ananth.narayan@....com>, Sandipan Das <sandipan.das@....com>
Subject: Re: [PATCH 01/11] perf/amd/ibs: Throttle interrupts with filtered
 ldlat samples


On 1/16/2026 11:34 AM, Ravi Bangoria wrote:
> IBS NMI handler has a software filter (on top of hardware filter) to
> discard samples with load latency value lesser than user requested
> threshold. However, since software filter still involves NMI, check
> for NMI overhead and throttle the sample rate if needed.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
>  arch/x86/events/amd/ibs.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
> index aca89f23d2e0..96bb0974057f 100644
> --- a/arch/x86/events/amd/ibs.c
> +++ b/arch/x86/events/amd/ibs.c
> @@ -1293,8 +1293,10 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
>  		 * within [128, 2048] range.
>  		 */
>  		if (!op_data3.ld_op || !op_data3.dc_miss ||
> -		    op_data3.dc_miss_lat <= (event->attr.config1 & 0xFFF))
> +		    op_data3.dc_miss_lat <= (event->attr.config1 & 0xFFF)) {
> +			throttle = perf_event_account_interrupt(event);
>  			goto out;
> +		}
>  	}

Not quite familiar with IBS code, but should the below code call the
throttle as well?

        /* Workaround for erratum #1197 */
        if (perf_ibs->fetch_ignore_if_zero_rip && !(ibs_data.regs[1]))
            goto out;


>  
>  	/*