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Wed, 15 Nov 2023 06:16:19 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9D3F2004D; Wed, 15 Nov 2023 06:16:18 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AE6BF20043; Wed, 15 Nov 2023 06:16:16 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by smtpav04.fra02v.mail.ibm.com (Postfix) with SMTP; Wed, 15 Nov 2023 06:16:16 +0000 (GMT) Date: Wed, 15 Nov 2023 11:46:16 +0530 From: Srikar Dronamraju To: "Aneesh Kumar K.V" Subject: Re: [PATCH v4 0/5] powerpc/smp: Topology and shared processor optimizations Message-ID: <20231115061616.dp5id27xip5j3ovl@linux.vnet.ibm.com> References: <20231109054938.26589-1-srikar@linux.vnet.ibm.com> <87v8a3zhl8.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <87v8a3zhl8.fsf@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: DSSAV-iQ-3SVHXm6L-w9TZNu66cVgEyZ X-Proofpoint-ORIG-GUID: z_IZwuVAVLgHDS3lQOTvEUUGU-0vSFZX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-15_04,2023-11-14_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 suspectscore=0 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 mlxlogscore=968 mlxscore=0 adultscore=0 bulkscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311150046 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Srikar Dronamraju Cc: Mark Rutland , Valentin Schneider , Vincent Guittot , "Paul E. McKenney" , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Rohan McLure , linuxppc-dev , Josh Poimboeuf Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Aneesh Kumar K.V [2023-11-15 11:24:59]: > Srikar Dronamraju writes: > > > PowerVM systems configured in shared processors mode have some unique > > challenges. Some device-tree properties will be missing on a shared > > processor. Hence some sched domains may not make sense for shared processor > > systems. > > > > Most shared processor systems are over-provisioned. Underlying PowerVM > > Hypervisor would schedule at a Big Core granularity. The most recent power > > processors support two almost independent cores. In a lightly loaded > > condition, it helps the overall system performance if we pack to lesser > > number of Big Cores. > > > > Is this good to do if the systems are not over-provisioned? What will be > the performance impact in that case with and without the change? > We are consolidating 1 thread per thread group (aka SMT domain). Since each thread-group is suppose to be independent including having a private L1/L2/L3 cache, we expect minimal impact in non over provisioned scenario. In Over utilization scenario, the changes in this patchset will not even kick in. -- Thanks and Regards Srikar Dronamraju