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Mon, 1 Dec 2025 12:15:38 +0000 (GMT) Date: Mon, 1 Dec 2025 17:45:37 +0530 From: Srikar Dronamraju To: Vincent Guittot Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ben Segall , Christophe Leroy , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Madhavan Srinivasan , Mel Gorman , Michael Ellerman , Nicholas Piggin , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Valentin Schneider Subject: Re: [PATCH v2 2/2] powerpc/smp: Disable steal from updating CPU capacity Message-ID: Reply-To: Srikar Dronamraju References: <20251029060757.2007601-1-srikar@linux.ibm.com> <20251029060757.2007601-2-srikar@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: HNs7Y5ATDJRfXHPva5QLC9S__2RJjgkN X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTI5MDAwOCBTYWx0ZWRfX+gGdOfJ1Z5UN ADdMqsTzCZijIQNCIDpG4gGmLZB8KPoGYXEJgYBCCMlJFDpxgCrBTk/grWwIpLMRaWz7a8Cu4mN qpo4Y3gQIETv4OtvHmHyTm14xTlZyBIEjBl01cmq7fFy/UItJBaSRijspyjm6bMstk606Shoujv ivTfsYRrETS3fUHDHe0c35Qq4+FfKtFkOGm49kC9ujO1mUtr7fBjERjAbgkNoyanmXJAkVs/wQC mrCP1KLRKQMoqpXIkyjv9X8gZWYXtEoGBMrukewJjU8NNQYk2z8dT7sC6v8JppHM/MMUGANbSte x0tvVs8S0Pb8wXqgI+TT5zL17lVpkBKr2CmYPDI+3Lo1g7RQM9x1WkIclv7oXTOWehEX+mq83Hi xTcrBKwCxNx89zUh2IYhiBdq2JJZ9w== X-Authority-Analysis: v=2.4 cv=Scz6t/Ru c=1 sm=1 tr=0 ts=692d86f4 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=8nJEP1OIZ-IA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=KKAkSRfTAAAA:8 a=VnNF1IyMAAAA:8 a=aOk6NyUQ4sEGh1re8dIA:9 a=wPNLvfGTeEIA:10 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-GUID: jmidmTeuBNEF7zmVGgWupDBfbwogCPbu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-28_08,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 clxscore=1015 spamscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511290008 * Vincent Guittot [2025-11-03 09:46:26]: > Hi Sikar, > > On Wed, 29 Oct 2025 at 09:32, Srikar Dronamraju wrote: > > > > * Vincent Guittot [2025-10-29 08:43:34]: > > > > > Hi Srikar, > > > > > > On Wed, 29 Oct 2025 at 07:09, Srikar Dronamraju wrote: > > > > > > > > In a shared LPAR with SMT enabled, it has been observed that when a CPU > > > > experiences steal time, it can trigger task migrations between sibling > > > > CPUs. The idle CPU pulls a runnable task from its sibling that is > > > > impacted by steal, making the previously busy CPU go idle. This reversal > > > > > > IIUC, the migration is triggered by the reduced capacity case when > > > there is 1 task on the CPU Hi Peter, Vincent Do you have any more inputs on this? If not can this pulled into the scheduler code. -- Thanks and Regards Srikar Dronamraju