From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Yicong Yang <yangyicong@huawei.com>,
catalin.marinas@arm.com, will@kernel.org, sudeep.holla@arm.com,
linux-arm-kernel@lists.infradead.org
Cc: yangyicong@hisilicon.com, gregkh@linuxfoundation.org,
rafael@kernel.org, jonathan.cameron@huawei.com,
prime.zeng@hisilicon.com, linuxarm@huawei.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch_topology: Support SMT control on arm64
Date: Fri, 22 Sep 2023 13:13:35 +0200 [thread overview]
Message-ID: <2247ced8-c4f9-80a7-a0a2-0953abed135f@arm.com> (raw)
In-Reply-To: <80b2556c-b56c-ca23-22c7-70a0a3995701@huawei.com>
On 21/09/2023 10:56, Yicong Yang wrote:
> On 2023/9/21 1:08, Dietmar Eggemann wrote:
>> On 19/09/2023 14:33, Yicong Yang wrote:
>>> From: Yicong Yang <yangyicong@hisilicon.com>
[...]
> If you manually disable SMT by offline each CPUs the cpu_smt_control will
> not be updated. It'll updated when using the interface like
> `/sys/devices/system/cpu/smt/control` or cmdline. By these means,
> the framework will use topology_is_primary_thread() to decide which CPU
> in the SMT will keep online:
>
> // e.g. echo off > /sys/devices/system/cpu/smt/control
> [ kernel/cpu.c ]
> control_store()
> __store_smt_control()
> cpuhp_smt_disable()
> for_each_online_cpu(cpu)
> if (topology_is_primary_thread(cpu))
> continue; <---------- will skip the primary thread
> [...]
> cpu_smt_control = CPU_SMT_DISABLED;
>
> topology_is_primary_thread() checking only applies to the SMT control but
> not to the CPU offline.
I see, make sense. Retested on my SMT4 Arm64 server with 256 CPUs.
next prev parent reply other threads:[~2023-09-22 11:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-19 12:33 [PATCH] arch_topology: Support SMT control on arm64 Yicong Yang
2023-09-19 23:30 ` kernel test robot
2023-09-20 1:36 ` Yicong Yang
2023-09-20 17:08 ` Dietmar Eggemann
2023-09-21 8:56 ` Yicong Yang
2023-09-22 11:13 ` Dietmar Eggemann [this message]
2023-09-21 15:03 ` Sudeep Holla
2023-09-22 9:46 ` Yicong Yang
2023-09-27 11:53 ` Yicong Yang
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