linux-kernel - Re: [PATCH V2 06/15] s390/perf: Remove driver-specific throttle support

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Message-ID: <ec0827aa-0bae-4625-ad60-f1a1765a4811@linux.ibm.com>
Date: Thu, 15 May 2025 15:15:54 +0200
From: Thomas Richter <tmricht@...ux.ibm.com>
To: kan.liang@...ux.intel.com, peterz@...radead.org, mingo@...hat.com,
        namhyung@...nel.org, irogers@...gle.com, mark.rutland@....com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Cc: eranian@...gle.com, ctshao@...gle.com, linux-s390@...r.kernel.org
Subject: Re: [PATCH V2 06/15] s390/perf: Remove driver-specific throttle
 support

On 5/14/25 17:13, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> The throttle support has been added in the generic code. Remove
> the driver-specific throttle support.
> 
> Besides the throttle, perf_event_overflow may return true because of
> event_limit. It already does an inatomic event disable. The pmu->stop
> is not required either.
> 
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> Cc: Thomas Richter <tmricht@...ux.ibm.com>
> Cc: linux-s390@...r.kernel.org
> ---
>  arch/s390/kernel/perf_cpum_cf.c | 2 --
>  arch/s390/kernel/perf_cpum_sf.c | 5 +----
>  2 files changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
> index e657fad7e376..6a262e198e35 100644
> --- a/arch/s390/kernel/perf_cpum_cf.c
> +++ b/arch/s390/kernel/perf_cpum_cf.c
> @@ -980,8 +980,6 @@ static int cfdiag_push_sample(struct perf_event *event,
>  	}
>  
>  	overflow = perf_event_overflow(event, &data, &regs);
> -	if (overflow)
> -		event->pmu->stop(event, 0);
>  
>  	perf_event_update_userpage(event);
>  	return overflow;
> diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
> index ad22799d8a7d..91469401f2c9 100644
> --- a/arch/s390/kernel/perf_cpum_sf.c
> +++ b/arch/s390/kernel/perf_cpum_sf.c
> @@ -1072,10 +1072,7 @@ static int perf_push_sample(struct perf_event *event,
>  	overflow = 0;
>  	if (perf_event_exclude(event, &regs, sde_regs))
>  		goto out;
> -	if (perf_event_overflow(event, &data, &regs)) {
> -		overflow = 1;
> -		event->pmu->stop(event, 0);
> -	}
> +	overflow = perf_event_overflow(event, &data, &regs);
>  	perf_event_update_userpage(event);
>  out:
>  	return overflow;

I have installed patch 1 and 6 on top of the linux-next kernel today.
The results look good, much better than before, but I still do not
get both counter values in sync on each iteration all the time.

Tested-by: Thomas Richter <tmricht@...ux.ibm.com>

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

Vorsitzender des Aufsichtsrats: Wolfgang Wendt

Geschäftsführung: David Faller

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