linux-kernel - [PATCH V2 0/2] Add complex scheduler level for arm64

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Message-ID: <SL2PR06MB3082D393ADEC823426DEE7DFBDFB9@SL2PR06MB3082.apcprd06.prod.outlook.com>
Date:   Tue, 26 Apr 2022 03:06:07 +0000
From:   王擎 <wangqing@...o.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>
Subject: [PATCH V2 0/2] Add complex scheduler level for arm64


>> From: Wang Qing <wangqing@...o.com>
>> 
>> The DSU cluster supports blocks that are called complexes
>> which contain up to two cores of the same type and some shared logic,
>> which sharing some logic between the cores can make a complex area efficient.
>>
>
>Given the complex shares things like the SVE units (cortex a510)...
>
>Why not handle this as SMT?

SMT should share all cache levels. but complexs only share L2(and L3)
cache here.

>
>Seems like a blurred boundary between separate cores and SMT threads.
>I think we need to express and potentially take advantage of knowledge
>about what logic is being shared.

Logic such as a Vector Processing Unit, L2 Translation Lookaside Buffer
(TLB) ... are shared, I believe this will improve efficiency even if
only L2 cache is shared.

Thanks,
Qing

>
>Jonathan
>
>> Complex also can be considered as a shared cache group smaller
>> than cluster.
>> 
>> This patch adds complex level for complexs by parsing cache topology
>> form DT. It will directly benefit a lot of workload which loves more
>> resources such as memory bandwidth, caches.
>> 
>> Note this patch only handle the DT case.
>> 
>> V2:
>> fix commit log and loop more
>> 
>> wangqing (2):
>>   arch_topology: support for describing cache topology from DT
>>   arm64: Add complex scheduler level for arm64
>> 
>>  arch/arm64/Kconfig            | 13 ++++++++++
>>  arch/arm64/kernel/smp.c       | 48 ++++++++++++++++++++++++++++++++++-
>>  drivers/base/arch_topology.c  | 47 +++++++++++++++++++++++++++++++++-
>>  include/linux/arch_topology.h |  3 +++
>>  4 files changed, 109 insertions(+), 2 deletions(-)
>>