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Mon, 7 Jul 2025 18:19:20 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CF1C62004B; Mon, 7 Jul 2025 18:19:20 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A02B920040; Mon, 7 Jul 2025 18:19:18 +0000 (GMT) Received: from [9.39.27.83] (unknown [9.39.27.83]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 7 Jul 2025 18:19:18 +0000 (GMT) Message-ID: <6e274729-af12-4e0f-9e67-5f2d5b099e99@linux.ibm.com> Date: Mon, 7 Jul 2025 23:49:17 +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 v2 00/12] sched: Address schbench regression From: Shrikanth Hegde To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, clm@meta.com References: <20250702114924.091581796@infradead.org> <132949bc-f901-40e6-a34c-d1d67d03d8b6@linux.ibm.com> Content-Language: en-US In-Reply-To: <132949bc-f901-40e6-a34c-d1d67d03d8b6@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzA3MDExOSBTYWx0ZWRfX8Qc1spvMgS0P tV+oiqif3D6tofA8tkf2BXAFUNpoQBJZQ+gJH3CtyPzZcIVjHCfPH5eiTKh1h5JxC+N2V5zyDkr akpiajZPe7KTQ4XyDEUqeAUXK1WjZgRriQ2QIih39qxy4C7eVZ1HNmS5+FrGs7aGSBBI1iQl6ux drGUUSzrPCBdWlXJSB4HsmDgrsxKMxavdBbCRHYMreBXsFQCbrPLWgtYfR9TpZdlzt0zSJxkV4/ 0EyeOHNpZ2Nx/7bFMJRBtJMafbSvmn1Kx4pg1AeVeYSsT5DoBNiOF1eiQKM0uAYURjqSA8vT8cs bcd2TITYbcb+BynKEDoZJKm8MYJQMaWI4vm7ahCA6cIJBagHaLS2J9s/oTTsnxKS9oyVD7knbtY LFOEdHu4A2WFW6/ALPcRY41bnEJLotrEZ2RLIbKjLYBFC/HRaPTbhuMG/a3ZqZiVNiPHUFCe X-Proofpoint-GUID: fIJ36tKNIsh3ktdaB2HcY3cJkncCQ1Qu X-Proofpoint-ORIG-GUID: sDt5DwP3TwtXWSfY_TBm_s2x285IOgns X-Authority-Analysis: v=2.4 cv=W/M4VQWk c=1 sm=1 tr=0 ts=686c0fac cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=VwQbUJbxAAAA:8 a=JfrnYn6hAAAA:8 a=ijCQEoXl7D5pwIERQb8A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-07-07_04,2025-07-07_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 mlxscore=0 priorityscore=1501 adultscore=0 clxscore=1015 suspectscore=0 spamscore=0 lowpriorityscore=0 mlxlogscore=592 bulkscore=0 impostorscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507070119 On 7/7/25 14:35, Shrikanth Hegde wrote: > > > On 7/2/25 17:19, Peter Zijlstra wrote: >> Hi! >> >> Previous version: >> >>    https://lkml.kernel.org/r/20250520094538.086709102@infradead.org >> >> >> Changes: >>   - keep dl_server_stop(), just remove the 'normal' usage of it (juril) >>   - have the sched_delayed wake list IPIs do select_task_rq() (vingu) >>   - fixed lockdep splat (dietmar) >>   - added a few preperatory patches >> >> >> Patches apply on top of tip/master (which includes the disabling of >> private futex) >> and clm's newidle balance patch (which I'm awaiting vingu's ack on). >> >> Performance is similar to the last version; as tested on my SPR on >> v6.15 base: >> > > > Hi Peter, > Gave this a spin on a machine with 5 cores (SMT8) PowerPC system. > > I see significant regression in schbench. let me know if i have to test > different > number of threads based on the system size. > Will go through the series and will try a bisect meanwhile. > > Used "./schbench -L -m 4 -M auto -t 64 -n 0 -t 60 -i 60" for git bisect. Also kept HZ=1000 Git bisect points to # first bad commit: [dc968ba0544889883d0912360dd72d90f674c140] sched: Add ttwu_queue support for delayed tasks Note: at commit: "sched: Change ttwu_runnable() vs sched_delayed" there is a small regression. ------------------------------------- Numbers at different commits: ------------------------------------- commit 8784fb5fa2e0042fe3b1632d4876e1037b695f56 <<<< baseline Merge: 11119b0b378a 94b59d5f567a Author: Borislav Petkov (AMD) Date: Sat Jul 5 19:24:35 2025 +0200 Merge irq/drivers into tip/master Wakeup Latencies percentiles (usec) runtime 30 (s) (39778894 total samples) 50.0th: 14 (11798914 samples) 90.0th: 27 (15931329 samples) * 99.0th: 42 (3032865 samples) 99.9th: 64 (346598 samples) RPS percentiles (requests) runtime 30 (s) (31 total samples) 20.0th: 1394688 (18 samples) * 50.0th: 1394688 (0 samples) 90.0th: 1398784 (11 samples) -------------------------------------- commit 88ca74dd6fe5d5b03647afb4698238e4bec3da39 (HEAD) <<< Still good commit Author: Peter Zijlstra Date: Wed Jul 2 13:49:34 2025 +0200 sched: Use lock guard in sched_ttwu_pending() Wakeup Latencies percentiles (usec) runtime 30 (s) (40132792 total samples) 50.0th: 14 (11986044 samples) 90.0th: 27 (15143836 samples) * 99.0th: 46 (3267133 samples) 99.9th: 72 (333940 samples) RPS percentiles (requests) runtime 30 (s) (31 total samples) 20.0th: 1402880 (23 samples) * 50.0th: 1402880 (0 samples) 90.0th: 1406976 (8 samples) ----------------------------------------------------------------- commit 755d11feca4544b4bc6933dcdef29c41585fa747 <<< There is a small regression. Author: Peter Zijlstra Date: Wed Jul 2 13:49:35 2025 +0200 sched: Change ttwu_runnable() vs sched_delayed Wakeup Latencies percentiles (usec) runtime 30 (s) (39308991 total samples) 50.0th: 18 (12991812 samples) 90.0th: 34 (14381736 samples) * 99.0th: 56 (3399332 samples) 99.9th: 84 (342508 samples) RPS percentiles (requests) runtime 30 (s) (31 total samples) 20.0th: 1353728 (21 samples) * 50.0th: 1353728 (0 samples) 90.0th: 1357824 (10 samples) ----------------------------------------------------------- commit dc968ba0544889883d0912360dd72d90f674c140 <<<< Major regression Author: Peter Zijlstra Date: Wed Jul 2 13:49:36 2025 +0200 sched: Add ttwu_queue support for delayed tasks Wakeup Latencies percentiles (usec) runtime 30 (s) (19818598 total samples) 50.0th: 111 (5891601 samples) 90.0th: 214 (7947099 samples) * 99.0th: 283 (1749294 samples) 99.9th: 329 (177336 samples) RPS percentiles (requests) runtime 30 (s) (31 total samples) 20.0th: 654336 (7 samples) * 50.0th: 660480 (11 samples) 90.0th: 666624 (11 samples)