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[90.13.240.27]) by smtp.gmail.com with ESMTPSA id a20sm16373190wmb.27.2021.12.29.02.44.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Dec 2021 02:44:33 -0800 (PST) Message-ID: <084c5004-6eb6-9952-0d9c-6ae3dc69aca0@redhat.com> Date: Wed, 29 Dec 2021 11:44:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH v5 02/14] hw/core/machine: Introduce CPU cluster topology support To: "wangyanan (Y)" , qemu-devel@nongnu.org, qemu-arm@nongnu.org References: <20211228092221.21068-1-wangyanan55@huawei.com> <20211228092221.21068-3-wangyanan55@huawei.com> <2248a06d-7c3d-2ee3-e683-901d9bcbec02@huawei.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: <2248a06d-7c3d-2ee3-e683-901d9bcbec02@huawei.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -63 X-Spam_score: -6.4 X-Spam_bar: ------ X-Spam_report: (-6.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.573, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-3.024, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , Peter Maydell , Andrew Jones , "Michael S . Tsirkin" , wanghaibin.wang@huawei.com, Markus Armbruster , Shannon Zhao , Igor Mammedov , Ani Sinha , Paolo Bonzini , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/29/21 04:48, wangyanan (Y) wrote: > Hi Philippe, > Thanks for your review. > > On 2021/12/29 3:17, Philippe Mathieu-Daudé wrote: >> Hi, >> >> On 12/28/21 10:22, Yanan Wang wrote: >>> The new Cluster-Aware Scheduling support has landed in Linux 5.16, >>> which has been proved to benefit the scheduling performance (e.g. >>> load balance and wake_affine strategy) on both x86_64 and AArch64. >>> >>> So now in Linux 5.16 we have four-level arch-neutral CPU topology >>> definition like below and a new scheduler level for clusters. >>> struct cpu_topology { >>>      int thread_id; >>>      int core_id; >>>      int cluster_id; >>>      int package_id; >>>      int llc_id; >>>      cpumask_t thread_sibling; >>>      cpumask_t core_sibling; >>>      cpumask_t cluster_sibling; >>>      cpumask_t llc_sibling; >>> } >>> >>> A cluster generally means a group of CPU cores which share L2 cache >>> or other mid-level resources, and it is the shared resources that >>> is used to improve scheduler's behavior. From the point of view of >>> the size range, it's between CPU die and CPU core. For example, on >>> some ARM64 Kunpeng servers, we have 6 clusters in each NUMA node, >>> and 4 CPU cores in each cluster. The 4 CPU cores share a separate >>> L2 cache and a L3 cache tag, which brings cache affinity advantage. >>> >>> In virtualization, on the Hosts which have pClusters, if we can >> Maybe [*] -> reference to pClusters? > Hm, I'm not sure what kind of reference is appropriate here. So I guess the confusion comes from a simple typo =) Is it OK if I replace "pClusters" by "Clusters"? > The third paragraph in the commit message has explained what > a cluster generally means. We can also read the description of > clusters in Linux kernel Kconfig files: [1] and [2]. > > [1]arm64: https://github.com/torvalds/linux/blob/master/arch/arm64/Kconfig > > config SCHED_CLUSTER >        bool "Cluster scheduler support" >        help >          Cluster scheduler support improves the CPU scheduler's decision >          making when dealing with machines that have clusters of CPUs. >          Cluster usually means a couple of CPUs which are placed closely >          by sharing mid-level caches, last-level cache tags or internal >          busses. > > [2]x86: https://github.com/torvalds/linux/blob/master/arch/x86/Kconfig > > config SCHED_CLUSTER >        bool "Cluster scheduler support" >        depends on SMP >        default y >        help >          Cluster scheduler support improves the CPU scheduler's decision >          making when dealing with machines that have clusters of CPUs. >          Cluster usually means a couple of CPUs which are placed closely >          by sharing mid-level caches, last-level cache tags or internal >          busses. >>> design a vCPU topology with cluster level for guest kernel and >>> have a dedicated vCPU pinning. A Cluster-Aware Guest kernel can >>> also make use of the cache affinity of CPU clusters to gain >>> similar scheduling performance. >>> >>> This patch adds infrastructure for CPU cluster level topology >>> configuration and parsing, so that the user can specify cluster >>> parameter if their machines support it. >>> >>> Signed-off-by: Yanan Wang >>> --- >>>   hw/core/machine-smp.c | 26 +++++++++++++++++++------- >>>   hw/core/machine.c     |  3 +++ >>>   include/hw/boards.h   |  6 +++++- >>>   qapi/machine.json     |  5 ++++- >>>   qemu-options.hx       |  7 ++++--- >>>   softmmu/vl.c          |  3 +++ >>>   6 files changed, 38 insertions(+), 12 deletions(-) >>> diff --git a/qapi/machine.json b/qapi/machine.json >>> index edeab6084b..ff0ab4ca20 100644 >>> --- a/qapi/machine.json >>> +++ b/qapi/machine.json >>> @@ -1404,7 +1404,9 @@ >>>   # >>>   # @dies: number of dies per socket in the CPU topology >>>   # >>> -# @cores: number of cores per die in the CPU topology >>> +# @clusters: number of clusters per die in the CPU topology >> Missing: >> >>     #            (since 7.0) > Ah, yes. >>> +# >>> +# @cores: number of cores per cluster in the CPU topology >>>   # >>>   # @threads: number of threads per core in the CPU topology >>>   # >>> @@ -1416,6 +1418,7 @@ >>>        '*cpus': 'int', >>>        '*sockets': 'int', >>>        '*dies': 'int', >>> +     '*clusters': 'int', >>>        '*cores': 'int', >>>        '*threads': 'int', >>>        '*maxcpus': 'int' } } >> If you want I can update the doc when applying. > Do you mean the missing "since 7.0"? > If you have a plan to apply the first 1-7 patches separately and > I don't need to respin, please help to update it, thank you! :) Yes, that is the plan. > > Thanks, > Yanan >> Thanks, >> >> Phil. >> >> . >