From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61BB9266EE6 for ; Mon, 14 Jul 2025 17:54:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752515699; cv=none; b=GwDnrng9JNduUh03YBh1Yag+HT+NYfy6a99jeA8bKJlMeSdQnBg/F9cWEXp6j9Bye2G7TV1r1RaTWFo+/uLps6Xq41n94VZbclZlJ/EFjzgJRXrbRF+vPIKiWYFuq2VGqIRZL7q4YdHQO7893/p+7oLqkFKHkJcJ4ITFZY6q5hU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752515699; c=relaxed/simple; bh=pg1YBiSHpDuyRVtex2aVCqbMAoM5OOsJMM5CKWlCDDc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JaCy4ldwt9yuEuupXSCIMSTJ0d89xJFy4ymhq/u3XuxqNlqn/KPgbc8J12CH2bbs1VnWV1rB1bWuOKY2WC6VFB7BI2tu0+JZphNtQunuqwTJ9+TmbNqcGwVVcUOOI+binemD3uaxL+kTSUShA9gtBdZMUsFe3F5igtWGfOMecvo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=DIIEsO4I; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="DIIEsO4I" Received: from pps.filterd (m0353725.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 56EDDBWD027341; Mon, 14 Jul 2025 17:54:43 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=U3xqp+ l4cxuc7XXP6umAs8/qOEzrVNYfnfN7JQuZcE8=; b=DIIEsO4I3aZvUh6mM+rM3N dFZGK3OOj0XVBSYtdpUHVwn38ocnPPoXk3eL5PmCmIUBN6sd8WQUKyBV4NyD99OM fPlOyfO/h9OBrYOhJN2tZsLycH3/SIIHy7dAHIzncDNreIllLFEBPgG+DcXCh93l 4cQJyMRrTOIdeLE1HAiCpPUlfB0P/mmKviFoVWZafRTEzjn0i6QGaXHemfIEc7nx KGgbnmdrik0OZNpc5ZgN19FvnOdZP3PXsBGmS9GTWpStw4iUw/YQPnYD+uekSyVb QxqkbFNJ8FWa9oTvD7sHMYrp2ziMK1Kt3Ac+MrNcGu2UjZFMfx6dmczB7krfx+fw == Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 47ue4tty1x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Jul 2025 17:54:42 +0000 (GMT) Received: from m0353725.ppops.net (m0353725.ppops.net [127.0.0.1]) by pps.reinject (8.18.0.8/8.18.0.8) with ESMTP id 56EHVBwK015968; Mon, 14 Jul 2025 17:54:42 GMT Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 47ue4tty1v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Jul 2025 17:54:42 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 56EHTImN008154; Mon, 14 Jul 2025 17:54:41 GMT Received: from smtprelay04.fra02v.mail.ibm.com ([9.218.2.228]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 47v2e0f321-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 14 Jul 2025 17:54:41 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 56EHsdFc16318770 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 14 Jul 2025 17:54:39 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 647AE2004B; Mon, 14 Jul 2025 17:54:39 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 216DF20040; Mon, 14 Jul 2025 17:54:37 +0000 (GMT) Received: from [9.124.219.62] (unknown [9.124.219.62]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 14 Jul 2025 17:54:36 +0000 (GMT) Message-ID: Date: Mon, 14 Jul 2025 23:24:36 +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 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> <6e274729-af12-4e0f-9e67-5f2d5b099e99@linux.ibm.com> <20250708190201.GE477119@noisy.programming.kicks-ass.net> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <20250708190201.GE477119@noisy.programming.kicks-ass.net> 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=baBrUPPB c=1 sm=1 tr=0 ts=68754462 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=irdw4SRykOf8dQUZ3u4A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: 0_5iLtn0nfm_dy4KhjaXynSfPyHdEFZT X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzE0MDExMiBTYWx0ZWRfX8srkMG/mFrxs oPxcrVQ8aCM6FLKYAzqlLSwJUARsytBYSxu3olD2JsSzEZqQI+kevJ8DSQ5EELpWIVBFhaDxwlg QI8kTmHZV+D4rkPmR7uM4OVYAs4soOHOsYmhLNwHgkrqg3cqYef+9HUVoDVs0H4rgi97ZD4V5dc owS4AlxA0Ch8F0kaqtGWyLM0Mki/bDiNdKwnoi8et6I0fHFL/1CKkKzZPPyolKg4IhclABnv3We mkvF2LMI3Yo5EozU9ElfLBj7MX5m9IXmrhkeLEZbNfr62P5uFogpngGlA2gN1jKBPNK5kdxFUAS yQ6OHa8JKoKBipVlGEbt3G32PU7kit8pyE4J/HpghzTeIDi+wsIj7YKfVyEL72/8MvkZZ+zHU7R WFQwylGt4hgExGyxewCNvo1urDluLVUJxks1/oZxvaQ+drqd/Vb33Vr8szpiPPQc2EqPzLB1 X-Proofpoint-ORIG-GUID: ftKuyZ9mRd4OQxvowLfjJMrsEXx7sPiy 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=2025-07-14_02,2025-07-14_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxlogscore=898 suspectscore=0 adultscore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 malwarescore=0 spamscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507140112 On 7/9/25 00:32, Peter Zijlstra wrote: > On Mon, Jul 07, 2025 at 11:49:17PM +0530, Shrikanth Hegde wrote: > >> Git bisect points to >> # first bad commit: [dc968ba0544889883d0912360dd72d90f674c140] sched: Add ttwu_queue support for delayed tasks > > Moo.. Are IPIs particularly expensive on your platform? > > The 5 cores makes me think this is a partition of sorts, but IIRC the > power LPAR stuff was fixed physical, so routing interrupts shouldn't be > much more expensive vs native hardware. > Some more data from the regression. I am looking at rps numbers while running ./schbench -L -m 4 -M auto -t 64 -n 0 -r 5 -i 5. All the data is from an LPAR(VM) with 5 cores. echo TTWU_QUEUE_DELAYED > features average rps: 970491.00 echo NO_TTWU_QUEUE_DELAYED > features current rps: 1555456.78 So below data points are with feature enabled or disabled with series applied + clm's patch. ------------------------------------------------------- ./hardirqs TTWU_QUEUE_DELAYED HARDIRQ TOTAL_usecs env2 816 IPI-2 1421603 << IPI are less compared to with feature. NO_TTWU_QUEUE_DELAYED HARDIRQ TOTAL_usecs ibmvscsi 8 env2 266 IPI-2 6489980 ------------------------------------------------------- Disabled all the idle states. Regression still exits. ------------------------------------------------------- See this warning everytime i run schbench: This happens with PATCH 12/12 only. It is triggering this warning. Some clock update is getting messed up? 1637 static inline void assert_clock_updated(struct rq *rq) 1638 { 1639 /* 1640 * The only reason for not seeing a clock update since the 1641 * last rq_pin_lock() is if we're currently skipping updates. 1642 */ 1643 WARN_ON_ONCE(rq->clock_update_flags < RQCF_ACT_SKIP); 1644 } WARNING: kernel/sched/sched.h:1643 at update_load_avg+0x424/0x48c, CPU#6: swapper/6/0 CPU: 6 UID: 0 PID: 0 Comm: swapper/6 Kdump: loaded Not tainted 6.16.0-rc4+ #276 PREEMPT(voluntary) NIP: c0000000001cea60 LR: c0000000001d7254 CTR: c0000000001d77b0 REGS: c000000003a674c0 TRAP: 0700 Not tainted (6.16.0-rc4+) MSR: 8000000000021033 CR: 28008208 XER: 20040000 CFAR: c0000000001ce68c IRQMASK: 3 GPR00: c0000000001d7254 c000000003a67760 c000000001bc8100 c000000061915400 GPR04: c00000008c80f480 0000000000000005 c000000003a679b0 0000000000000000 GPR08: 0000000000000001 0000000000000000 c0000003ff14d480 0000000000004000 GPR12: c0000000001d77b0 c0000003ffff7880 0000000000000000 000000002eef18c0 GPR16: 0000000000000006 0000000000000006 0000000000000008 c000000002ca2468 GPR20: 0000000000000000 0000000000000004 0000000000000009 0000000000000001 GPR24: 0000000000000000 0000000000000001 0000000000000001 c0000003ff14d480 GPR28: 0000000000000001 0000000000000005 c00000008c80f480 c000000061915400 NIP [c0000000001cea60] update_load_avg+0x424/0x48c LR [c0000000001d7254] enqueue_entity+0x5c/0x5b8 Call Trace: [c000000003a67760] [c000000003a677d0] 0xc000000003a677d0 (unreliable) [c000000003a677d0] [c0000000001d7254] enqueue_entity+0x5c/0x5b8 [c000000003a67880] [c0000000001d7918] enqueue_task_fair+0x168/0x7d8 [c000000003a678f0] [c0000000001b9554] enqueue_task+0x5c/0x1c8 [c000000003a67930] [c0000000001c3f40] ttwu_do_activate+0x98/0x2fc [c000000003a67980] [c0000000001c4460] sched_ttwu_pending+0x2bc/0x72c [c000000003a67a60] [c0000000002c16ac] __flush_smp_call_function_queue+0x1a0/0x750 [c000000003a67b10] [c00000000005e1c4] smp_ipi_demux_relaxed+0xec/0xf4 [c000000003a67b50] [c000000000057dd4] doorbell_exception+0xe0/0x25c [c000000003a67b90] [c0000000000383d0] __replay_soft_interrupts+0xf0/0x154 [c000000003a67d40] [c000000000038684] arch_local_irq_restore.part.0+0x1cc/0x214 [c000000003a67d90] [c0000000001b6ec8] finish_task_switch.isra.0+0xb4/0x2f8 [c000000003a67e30] [c00000000110fb9c] __schedule+0x294/0x83c [c000000003a67ee0] [c0000000011105f0] schedule_idle+0x3c/0x64 [c000000003a67f10] [c0000000001f27f0] do_idle+0x15c/0x1ac [c000000003a67f60] [c0000000001f2b08] cpu_startup_entry+0x4c/0x50 [c000000003a67f90] [c00000000005ede0] start_secondary+0x284/0x288 [c000000003a67fe0] [c00000000000e058] start_secondary_prolog+0x10/0x14 ---------------------------------------------------------------- perf stat -a: ( idle states enabled) TTWU_QUEUE_DELAYED: 13,612,930 context-switches # 0.000 /sec 912,737 cpu-migrations # 0.000 /sec 1,245 page-faults # 0.000 /sec 449,817,741,085 cycles 137,051,199,092 instructions # 0.30 insn per cycle 25,789,965,217 branches # 0.000 /sec 286,202,628 branch-misses # 1.11% of all branches NO_TTWU_QUEUE_DELAYED: 24,782,786 context-switches # 0.000 /sec 4,697,384 cpu-migrations # 0.000 /sec 1,250 page-faults # 0.000 /sec 701,934,506,023 cycles 220,728,025,829 instructions # 0.31 insn per cycle 40,271,327,989 branches # 0.000 /sec 474,496,395 branch-misses # 1.18% of all branches both cycles and instructions are low. ------------------------------------------------------------------- perf stat -a: ( idle states disabled) TTWU_QUEUE_DELAYED: 15,402,193 context-switches # 0.000 /sec 1,237,128 cpu-migrations # 0.000 /sec 1,245 page-faults # 0.000 /sec 781,215,992,865 cycles 149,112,303,840 instructions # 0.19 insn per cycle 28,240,010,182 branches # 0.000 /sec 294,485,795 branch-misses # 1.04% of all branches NO_TTWU_QUEUE_DELAYED: 25,332,898 context-switches # 0.000 /sec 4,756,682 cpu-migrations # 0.000 /sec 1,256 page-faults # 0.000 /sec 781,318,730,494 cycles 220,536,732,094 instructions # 0.28 insn per cycle 40,424,495,545 branches # 0.000 /sec 446,724,952 branch-misses # 1.11% of all branches Since idle states are disabled, cycles are always spent on CPU. so cycles are more or less, while instruction differs. Does it mean with feature enabled, is there a lock(maybe rq) for too long? -------------------------------------------------------------------- Will try to gather more into why is this happening.