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Thu, 13 Aug 2026 11:12:05 +0000 (GMT) Received: from [9.123.5.233] (unknown [9.123.5.233]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 13 Aug 2026 11:12:05 +0000 (GMT) Message-ID: <20aa609c-6b11-41a1-875e-3aaba2809883@linux.ibm.com> Date: Thu, 13 Aug 2026 16:42:04 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Re: [PATCH v10 00/12] sched, steal_governor: Introduce preferred CPUs and steal-driven vCPU backoff To: Mete Durlu , Yury Norov , "Ionut Nechita (Sunlight Linux)" , frederic@kernel.org Cc: arighi@nvidia.com, chleroy@kernel.org, christian.loehle@arm.com, corbet@lwn.net, dietmar.eggemann@arm.com, gregkh@linuxfoundation.org, hdanton@sina.com, huschle@linux.ibm.com, iii@linux.ibm.com, jgross@suse.com, juri.lelli@redhat.com, kernellwp@gmail.com, kprateek.nayak@amd.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, maddy@linux.ibm.com, maz@kernel.org, mingo@kernel.org, pauld@redhat.com, pbonzini@redhat.com, peterz@infradead.org, rafael@kernel.org, rdunlap@infradead.org, rostedt@goodmis.org, seanjc@google.com, tglx@kernel.org, tj@kernel.org, tommaso.cucinotta@gmail.com, vincent.guittot@linaro.org, vineeth@bitbyteword.org, virtualization@lists.linux.dev, vschneid@redhat.com, yury.norov@gmail.com References: <20260812054033.95658-1-sshegde@linux.ibm.com> <20260812194600.52516-1-sunlightlinux@gmail.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=XqfK/1F9 c=1 sm=1 tr=0 ts=6a7da692 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=SfQhua3PvPfpT-rxooIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEzMDA3NyBTYWx0ZWRfX7ONJ2/yJPsWB DgAnuRW0kwGy+fH6og1mBsmFMrne7Jx5Z4NXebcJYvfCJBNr1lilBoc2JclTXcfJQ6YTioYr7Gs p2zA1+xolUe+5DaSBmZneSpHaXw1IcZJpHuwGE40X7UiUSdCeeDcEeHrqIb7gLM6w+eqkIqitcp 9hdzw06FmMixioG1FI7FjPJHSBDAvwQYg/1+SIGBeOlnECwmSXFe7TJZmFEAZWVnZS0U/W9nNUZ nUwsP+n69aDIP6UokVgfuXIP5lF4UXRQ/jSZF6aRp3AH5aq8r6q+bymvvXJ/CwcmVyig63JXKvN ogck2oF1jGD8z+vIowKBS1VFRQVLXlT9iAL3Mg1rB4OurAHgO60yNl+ehX4F772b9Z37XJ4yKik 3Gxqu2G83cgx6mFUep34cAIqjw2Q3qbFqNhkLyHPxlCh0auvRU2KOUFQEaEvjp4Qa9yCbOqfyXx +/Pz5ssUMqGIuTLFf+Q== X-Proofpoint-ORIG-GUID: sSnQb8kE7Qd8l6HXRkZpa6sRtJz5HmsN X-Proofpoint-GUID: ZGZ3zDi8DY8N3h9UafM1rLg_PPBgRmvN X-Proofpoint-Spam-Info: AW1haW4tMjYwODEzMDA3NyBTYWx0ZWRfX5K9JCZ2fQQI9 M6EByBaouIAWxS6kpyGy0is4BsStq5UypmIElikD2Aqbv3Vrp4UqWtiXsO+jXW0mGDZbmsyOK9u KIQvFPfMqTYmhlJq1hepZoM8QonLVB8= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-13_03,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 adultscore=0 malwarescore=0 clxscore=1015 suspectscore=0 priorityscore=1501 impostorscore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608130077 Hi Mete, Thanks for going through the patches/discussions. On 8/13/26 12:20 PM, Mete Durlu wrote: > Hi all, > > All of the points raised by Ionut are about governor lacking > certain logic for a specific arch. Considering what Shrikanth > mentions under "Future Work"; > > """ > Known Limitations & Future Work > =============================== > ... > - Arch specific hints and framework for it as been deferred to >   the future. > ... > """ > > I think all of these points can be addressed better if > Xen used said framework and implemented their own governor > module. That way we wouldn't see an overinflated single > steal_governor but instead nicely separated arch/platform > specific ones, that are tailored best for their needs. > The current implementation could be the fallback option > if platform does not implement their own and would also > serve as an example. For now, I prefer adding a defensive check for dom0 and keep the driver simple. > > I really think we should follow the example of cpuidle > drivers and how their framework brings together so many > platforms under a single roof. > But I remember fredric saying it isn't ideal either and he had planned to clean it up. (Fredric, correct me if i remember it wrong) > Thanks! > -Mete I prefer we defer the arch specific hooks for now, until there is a need for one. If you guys insist it should be done, then i can start looking at cpuidle framework. But it will be a bigger rework. But if the patch given in other thread is good enough for XEN, then we could keep it simple one file for the time being. If the driver eventually outgrows a single file, we can work on a modular framework post-merge. But for now, let's keep it simple and get the simple version upstream. Thoughts?