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Thu, 26 Feb 2026 12:57:32 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 61QCvSBK46727672 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 Feb 2026 12:57:28 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8C52B2004B; Thu, 26 Feb 2026 12:57:28 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4E71120040; Thu, 26 Feb 2026 12:57:22 +0000 (GMT) Received: from [9.39.17.58] (unknown [9.39.17.58]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 26 Feb 2026 12:57:22 +0000 (GMT) Message-ID: <129ebc98-6d1c-42c0-8e60-4072fa82719e@linux.ibm.com> Date: Thu, 26 Feb 2026 18:27:21 +0530 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle To: "Christophe Leroy (CS GROUP)" , Frederic Weisbecker , LKML , Madhavan Srinivasan Cc: "Rafael J. Wysocki" , Alexander Gordeev , Anna-Maria Behnsen , Ben Segall , Boqun Feng , Christian Borntraeger , Dietmar Eggemann , Heiko Carstens , Ingo Molnar , Jan Kiszka , Joel Fernandes , Juri Lelli , Kieran Bingham , Mel Gorman , Michael Ellerman , Neeraj Upadhyay , Nicholas Piggin , "Paul E . McKenney" , Peter Zijlstra , Steven Rostedt , Sven Schnelle , Thomas Gleixner , Uladzislau Rezki , Valentin Schneider , Vasily Gorbik , Vincent Guittot , Viresh Kumar , Xin Zhao , linux-pm@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20260206142245.58987-1-frederic@kernel.org> <20260206142245.58987-5-frederic@kernel.org> <9413517d-963b-4e6d-b11b-b440acd7cb5a@linux.ibm.com> <9ab1e7d7-57ee-49f9-963c-3a1b96dda684@kernel.org> <120884b0-0b09-43a9-b0f6-7dc2affe1ac0@linux.ibm.com> <1c1e5cf6-5b38-476c-ba49-35510312b064@kernel.org> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <1c1e5cf6-5b38-476c-ba49-35510312b064@kernel.org> 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-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI2MDExNCBTYWx0ZWRfX/CCnAH//3SmG Kt2gN8BfZiChmASyXp7/StDlt3jCLfHmVQRXLl/KLab/RNovFlrpa6FxRbrQ7q9iSiMwoChrC6M du5G1acoa2tbTo4xa/r2S5S042gvV5xjKvjzsFJ/9N9fsHD7CpOLibh1DoUg3auGGZjVX8MYtub 7hkGxbdtItlKGEUZoqzQSHzkWgEwWsmNeFFLJFwsgXg8jrg4i3YhOZkTLlOQNgJ/cwU7PP0UeRF iDG7QIsSJYoJEIRkdbx+iXnAziBjmZBh3UWYpDqrXcZewoixzuy3eE+nBezDgy+SMKJxzx0fkQD U/r2MsnigpfJNqmlSbzxKCZqqVoQ3mViVQpmzLQit+WsewNl+z14jCNyLa8fNz48pn+hd7q3fnR I9bx489bSyoaXIVHhkvmnNkUfb8xeeiBVqWo+f9BHq6vaeyFkuPl6F1R8fcmXzl+bgf+fqbXNla M8M0TV3Cu4eSQvcXwjQ== X-Proofpoint-ORIG-GUID: 7cmKtdgDQHK2cqD4DGWSagANoTD8iAKA X-Authority-Analysis: v=2.4 cv=F9lat6hN c=1 sm=1 tr=0 ts=69a0433e cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=zlYsBo3-bph3zESPOqkA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: eLrZGOqrYbJYs4jS4w0-JPJwZ3aBQmiF 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=2026-02-25_04,2026-02-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 bulkscore=0 adultscore=0 spamscore=0 clxscore=1015 suspectscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602260114 Hi Christophe. >> No. With this patch there will not be any performance difference. >> All it does is, instead of using mftb uses sched_clock at those places. >> > > For the record, I did some benchmark test with tools/testing/selftests/ > powerpc/benchmarks/null_syscall on powerpc 885 microcontroller: > > Without your proposed patch: > > root@vgoip:~# ./null_syscall >    2729.98 ns     360.36 cycles > > With your proposed patch below: > > root@vgoip:~# ./null_syscall >    3370.80 ns     444.95 cycles > > So as expected it is a huge regression, almost 25% more time to run the > syscall. > > Christophe > > >> Got it. My bad in assuming it may not happen multiple before vtime_flush. Btw, can you try latest vtime_reset patch? It shouldn't make any difference. I tried perf bench syscall basic, and ./null_syscall. I don't any difference for vtime_reset patch.