From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
To: Anton Blanchard <anton@ozlabs.org>
Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
ego@linux.vnet.ibm.com, rjw@rjwysocki.net,
daniel.lezcano@linaro.org, npiggin@gmail.com,
linuxppc-dev@lists.ozlabs.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority
Date: Tue, 4 Apr 2017 09:34:41 +0530 [thread overview]
Message-ID: <20170404040441.GB21029@drishya.in.ibm.com> (raw)
In-Reply-To: <20170403215414.16951-1-anton@ozlabs.org>
* Anton Blanchard <anton@ozlabs.org> [2017-04-04 07:54:12]:
> From: Anton Blanchard <anton@samba.org>
>
> The core of snooze_loop() continually bounces between low and very
> low thread priority. Changing thread priorities is an expensive
> operation that can negatively impact other threads on a core.
>
> All CPUs that can run PowerNV support very low priority, so we can
> avoid the change completely.
>
> Signed-off-by: Anton Blanchard <anton@samba.org>
Reviewed-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
> ---
> drivers/cpuidle/cpuidle-powernv.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index cda8f62d555b..9d9f164894eb 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -57,7 +57,6 @@ static int snooze_loop(struct cpuidle_device *dev,
> snooze_exit_time = get_tb() + snooze_timeout;
> ppc64_runlatch_off();
> while (!need_resched()) {
> - HMT_low();
> HMT_very_low();
> if (snooze_timeout_en && get_tb() > snooze_exit_time)
> break;
HMT_low() is legacy and can be removed for powernv platforms.
--Vaidy
prev parent reply other threads:[~2017-04-04 4:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-03 21:54 [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority Anton Blanchard
2017-04-03 21:54 ` [PATCH 2/3] cpuidle: powernv: Don't continually set thread priority in snooze_loop() Anton Blanchard
2017-04-04 4:06 ` Vaidyanathan Srinivasan
2017-04-03 21:54 ` [PATCH 3/3] cpuidle: powernv: Avoid a branch in the core snooze_loop() loop Anton Blanchard
2017-04-03 23:54 ` Nicholas Piggin
2017-04-04 4:10 ` Vaidyanathan Srinivasan
2017-04-03 23:52 ` [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority Nicholas Piggin
2017-04-04 4:13 ` Vaidyanathan Srinivasan
2017-04-04 4:04 ` Vaidyanathan Srinivasan [this message]
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