From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Anton Blanchard <anton@ozlabs.org>,
benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
ego@linux.vnet.ibm.com, rjw@rjwysocki.net,
daniel.lezcano@linaro.org, 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 09:43:43 +0530 [thread overview]
Message-ID: <20170404041343.GE21029@drishya.in.ibm.com> (raw)
In-Reply-To: <20170404095207.28fc5229@roar.ozlabs.ibm.com>
* Nicholas Piggin <npiggin@gmail.com> [2017-04-04 09:52:07]:
> On Tue, 4 Apr 2017 07:54:12 +1000
> Anton Blanchard <anton@ozlabs.org> wrote:
>
> > 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.
>
> This looks good. I have HMT_lowest() which does alt feature patching
> we can use for pseries and default idle code.
Alternatively, if we are going to set priority only once in various
other places, HMT_low(); HMT_very_low(); should not add to extra
cycles. Let me code that up.
--Vaidy
next prev parent reply other threads:[~2017-04-04 4:14 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 [this message]
2017-04-04 4:04 ` Vaidyanathan Srinivasan
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