From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Pratik Rajesh Sampat <psampat@linux.ibm.com>,
rjw@rjwysocki.net, mpe@ellerman.id.au, benh@kernel.crashing.org,
paulus@samba.org, srivatsa@csail.mit.edu, shuah@kernel.org,
npiggin@gmail.com, ego@linux.vnet.ibm.com, svaidy@linux.ibm.com,
pratik.r.sampat@gmail.com, linux-pm@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 0/2] Selftest for cpuidle latency measurement
Date: Tue, 21 Jul 2020 16:57:56 +0200 [thread overview]
Message-ID: <17e884b8-09d8-98a8-3890-bf506d2cdfca@linaro.org> (raw)
In-Reply-To: <20200721124300.65615-1-psampat@linux.ibm.com>
On 21/07/2020 14:42, Pratik Rajesh Sampat wrote:
> v2: https://lkml.org/lkml/2020/7/17/369
> Changelog v2-->v3
> Based on comments from Gautham R. Shenoy adding the following in the
> selftest,
> 1. Grepping modules to determine if already loaded
> 2. Wrapper to enable/disable states
> 3. Preventing any operation/test on offlined CPUs
> ---
>
> The patch series introduces a mechanism to measure wakeup latency for
> IPI and timer based interrupts
> The motivation behind this series is to find significant deviations
> behind advertised latency and resisdency values
Why do you want to measure for the timer and the IPI ? Whatever the
source of the wakeup, the exit latency remains the same, no ?
Is all this kernel-ish code really needed ?
What about using a highres periodic timer and make it expires every eg.
50ms x 2400, so it is 120 secondes and measure the deviation. Repeat the
operation for each idle states.
And in order to make it as much accurate as possible, set the program
affinity on a CPU and isolate this one by preventing other processes to
be scheduled on and migrate the interrupts on the other CPUs.
That will be all userspace code, no?
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next prev parent reply other threads:[~2020-07-21 15:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 12:42 [PATCH v3 0/2] Selftest for cpuidle latency measurement Pratik Rajesh Sampat
2020-07-21 12:42 ` [PATCH v3 1/2] cpuidle: Trace IPI based and timer based wakeup latency from idle states Pratik Rajesh Sampat
2020-07-27 13:42 ` Rafael J. Wysocki
2020-07-28 13:30 ` Pratik Sampat
2020-07-21 12:43 ` [PATCH v3 2/2] selftest/cpuidle: Add support for cpuidle latency measurement Pratik Rajesh Sampat
2020-07-21 14:57 ` Daniel Lezcano [this message]
2020-07-22 15:33 ` [PATCH v3 0/2] Selftest " Pratik Sampat
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