From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm64: Improve parking of stopped CPUs
Date: Wed, 1 Feb 2017 14:16:57 +0000 [thread overview]
Message-ID: <20170201141656.GB8177@arm.com> (raw)
In-Reply-To: <1485942532-2643-1-git-send-email-jnair@caviumnetworks.com>
On Wed, Feb 01, 2017 at 09:48:52AM +0000, Jayachandran C wrote:
> The current code puts the stopped cpus in an 'yield' instruction loop.
> Using a busy loop here is unnecessary, we can use the cpu_park_loop()
> function here to do a wfi/wfe.
>
> Signed-off-by: Jayachandran C <jnair@caviumnetworks•com>
> ---
> arch/arm64/kernel/smp.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index cbaab44..0691d2f 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -829,8 +829,7 @@ static void ipi_cpu_stop(unsigned int cpu)
>
> local_irq_disable();
>
> - while (1)
> - cpu_relax();
> + cpu_park_loop();
> }
Hmm, so we actually added the yield for QEMU's benefit iirc, where QEMU
will trap the yield and schedule a different vCPU. Should we be adding
a yield to cpu_park_loop instead?
Will
next prev parent reply other threads:[~2017-02-01 14:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-01 9:48 [PATCH] arm64: Improve parking of stopped CPUs Jayachandran C
2017-02-01 14:16 ` Will Deacon [this message]
2017-02-01 14:31 ` Suzuki K Poulose
2017-02-01 15:07 ` Will Deacon
2017-02-02 7:42 ` Jayachandran C
2019-05-16 18:44 ` Aaro Koskinen
2019-05-18 22:19 ` Jayachandran Chandrasekharan Nair
2019-05-18 23:12 ` Aaro Koskinen
2019-05-24 19:24 ` [EXT] " Jayachandran Chandrasekharan Nair
2019-05-23 10:05 ` Will Deacon
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