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Wed, 28 Jan 2026 06:26:56 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D0A8D20040; Wed, 28 Jan 2026 06:26:56 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3B8F020043; Wed, 28 Jan 2026 06:26:53 +0000 (GMT) Received: from [9.111.60.95] (unknown [9.111.60.95]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 28 Jan 2026 06:26:52 +0000 (GMT) Message-ID: <868b9993-34a2-4b33-b47a-989b2c680689@linux.ibm.com> Date: Wed, 28 Jan 2026 11:56:52 +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 v7] sched/clock: Avoid false sharing for sched_clock_irqtime To: K Prateek Nayak , "Guo, Wangyang" Cc: linux-kernel@vger.kernel.org, Benjamin Lei , Tim Chen , Tianyou Li , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider References: <20260127072509.2627346-1-wangyang.guo@intel.com> <7c6236a5-82b7-4d1b-9bb2-3f0d2ac186f8@linux.ibm.com> <3b69443c-f82c-4b73-8384-2a039d730213@intel.com> <5e001aeb-50a8-475f-bff2-6d101e15d078@amd.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <5e001aeb-50a8-475f-bff2-6d101e15d078@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Gr1PO01C c=1 sm=1 tr=0 ts=6979ac34 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=5u9vbh8bQKnAIdoEtWQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: LkE69vMzFFI2rzFryQTt5fQklPaQW_3w X-Proofpoint-ORIG-GUID: kzNU5mMJbpVPS6NH8ZGpCvDokb9_4sPk X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTI4MDA0OSBTYWx0ZWRfX9J8nBx4Ju118 GTrEVgXYykCJtooiGWlUbjXHCS7VfuCfK5PjRKWaPvdLjtzgAVLgyk33PvVk7qpXED8JHiwfG2f sPvPh1PJ/nrDFs14/dIHVG6ziwulgTizwYulLouX+uQlqBXFBD2PyzOnFUHqyHIQ4QLb6hHGNg3 Vg+jeOOqgyCBLB06uvjrLgzOmYYPokNkYK3ZWXDGnf+PE8lZIgQJEwGLtji8gurlpbla5vC5rOo C42ecdLdKNeXY6vMXt39YPgbfU0embXQT8Od0PY4z5KsoIMdakjrtTib6Dd696gY/lH0wiwbbLo LRbQ+ClWl0pE5r1uQyKCpf+/aeWC2k0ajbO1PSjq9sMrfW96EpydTMu0caKIerH45PQTqBuwnbP gQ13DAiy4G4mdmHb4hnfEa86MjmZruS2SC7zQtSx37oJDaRAPyA6do+FHm2YjxiSZltMLwG48Ux iYjEKTu2QAQqvAh6Uzw== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-01-27_05,2026-01-27_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 clxscore=1015 lowpriorityscore=0 suspectscore=0 impostorscore=0 phishscore=0 malwarescore=0 adultscore=0 spamscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601280049 On 1/28/26 8:35 AM, K Prateek Nayak wrote: > On 1/28/2026 7:49 AM, Guo, Wangyang wrote: >> Yes, when clock mark unstable through tsc_.*mark_unstable() with non-native_sched_clock, clear_sched_clock_stable won't be called, thus sched_clock_irqtime still keep enabled. >> >> Maybe the dedicated workqueue for sched_clock_irqtime is still needed considering this case. > > In that case, shouldn't tsc_init() only enable irqtime when > using_native_sched_clock()? How can tsc_init() make a call on irqtime if > TSC isn't being used as the sched_clock() ultimately? > > For kvmclock, if PVCLOCK_TSC_STABLE_BIT is not set, it'll call > clear_sched_clock_stable() at kvm_sched_clock_init() but none of the > other clocksources do so we can assume once we override the sched_clock() > it is up to the sched_clock() provider to deal with the clock stability. > I think this would depend if mark_tsc_unstable happens after system boot, specially while running kvm guest?