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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077058FBED0@SHSMSX103.ccr.corp.intel.com>
Date: Thu, 12 May 2016 13:26:53 +0000
From: "Liang, Kan" <kan.liang@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: "mingo@...hat.com" <mingo@...hat.com>,
"acme@...nel.org" <acme@...nel.org>,
"alexander.shishkin@...ux.intel.com"
<alexander.shishkin@...ux.intel.com>,
"ak@...ux.intel.com" <ak@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] perf/core: fix implicitly enable dynamic interrupt
throttle
>
>
> Hmm, would it not be nicer to simply reject the write instead of silently
> ignoring it?
>
Yes, I agree.
Thanks,
Kan
> ---
> kernel/events/core.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c index
> 050a290c72c7..0a51a568d4eb 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -396,6 +396,13 @@ int perf_proc_update_handler(struct ctl_table
> *table, int write,
> if (ret || !write)
> return ret;
>
> + /*
> + * If the throttling is disabled; don't allow the write.
> + */
> + if (sysctl_perf_cpu_time_max_percent == 100 ||
> + sysctl_perf_cpu_time_max_percent == 0)
> + return -EINVAL;
> +
> max_samples_per_tick =
> DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
> perf_sample_period_ns = NSEC_PER_SEC /
> sysctl_perf_event_sample_rate;
> update_perf_cpu_limits();
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