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Wed, 15 Nov 2023 05:42:53 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8E2A320040; Wed, 15 Nov 2023 05:42:53 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A70B120043; Wed, 15 Nov 2023 05:42:50 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by smtpav05.fra02v.mail.ibm.com (Postfix) with SMTP; Wed, 15 Nov 2023 05:42:50 +0000 (GMT) Date: Wed, 15 Nov 2023 11:12:49 +0530 From: Srikar Dronamraju To: "Aneesh Kumar K.V" Subject: Re: [PATCH v4 1/5] powerpc/smp: Enable Asym packing for cores on shared processor Message-ID: <20231115054249.GU2194132@linux.vnet.ibm.com> References: <20231109054938.26589-1-srikar@linux.vnet.ibm.com> <20231109054938.26589-2-srikar@linux.vnet.ibm.com> <87y1ezzivn.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <87y1ezzivn.fsf@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: zomlcP0pf8N65RFJnsp8mhL92_KTB0QJ X-Proofpoint-ORIG-GUID: MPLHRE2V3qDNbSDab5SXYdbHpWvDG23D 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 impostorscore=0 phishscore=0 malwarescore=0 adultscore=0 priorityscore=1501 clxscore=1015 suspectscore=0 bulkscore=0 mlxlogscore=955 lowpriorityscore=0 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311150042 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 , "ndesaulniers@google.com" , linux-kernel@vger.kernel.org, Rohan McLure , Nicholas Piggin , 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 10:57:08]: > Srikar Dronamraju writes: > > > If there are shared processor LPARs, underlying Hypervisor can have more > > virtual cores to handle than actual physical cores. > > > > Starting with Power 9, a big core (aka SMT8 core) has 2 nearly > > independent thread groups. On a shared processors LPARs, it helps to > > pack threads to lesser number of cores so that the overall system > > performance and utilization improves. PowerVM schedules at a big core > > level. Hence packing to fewer cores helps. > > > > For example: Lets says there are two 8-core Shared LPARs that are > > actually sharing a 8 Core shared physical pool, each running 8 threads > > each. Then Consolidating 8 threads to 4 cores on each LPAR would help > > them to perform better. This is because each of the LPAR will get > > 100% time to run applications and there will no switching required by > > the Hypervisor. > > > > Will this patch consolidate things to first 8 threads or just the one > Big core? /me continues to look at other patches and wonder whether 4/5 > should come before this? It will consolidate 1 thread per small core aka SMT domain or 2 threads per Big core. If the load is such that there are more unbound threads than SMT domains, asym packing will not kick-in. 4/5 would make sense only once we enable asym_packing above SMT domain. > > > > > > To achieve this, enable SD_ASYM_PACKING flag at CACHE, MC and DIE level > > when the system is running in shared processor mode and has big cores. > > > > Signed-off-by: Srikar Dronamraju > > > -aneesh -- Thanks and Regards Srikar Dronamraju