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 549671C5D57; Thu, 26 Feb 2026 12:05:18 +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=1772107519; cv=none; b=cJUmKLPpfFIVMP0qg5xaOoEwE3G8BUV3uQTQC80CRed+sZRt2LtdlNPOjXYD9u2IfD+efdTxOcZnZotbXxVUg3i7mou0OOveWE/TpDTUXiuz/ToqiYBUKEhMb2e1217iy85GypcWwBR8/u34t+/k2NpB/JWmpiS8M3XutxrEN0Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772107519; c=relaxed/simple; bh=bIGOu/hLDz+KosdYvExu/sl7yWLgOM4ExSWWmkQkA1M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KI406poiBNRdG0YDhzU95786KfOmjWmwsnIc9AI2N4Et4q2CXbXSgJh06BkQC0smI2ZNGoCqovjvHNkUwsBYxLmD7X9j/eEWRz/rN+bFvb+B7EGoPOQbm1NgfYEV5A1UQhLDtPb0iG83DTPwLcKxuLaM+ng6cilUIZbokmDVRrc= 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=jLHmlcS9; 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="jLHmlcS9" Received: from pps.filterd (m0356516.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 61Q7dVOV1887407; Thu, 26 Feb 2026 12:04:31 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to; s=pp1; bh=ANcZNjIxQSI14Z7YPaEcHfoSZWvSU/ YHaFbMJhg7PNQ=; b=jLHmlcS94bfiJNIjThTQYWAfZI8pysuAPgHyjDQn29/kxU Yc4qEuOF7oHEezSZLiApUGKKC02/hzl1Ml3+Mgt9MfHsLXPhEkOp7ija10bqoivW AYOxzw4uxI2uL7z67ln2IqOylxwdjEjrnE7LzetIx5Tdj3z7w3ICLSfQabjkwHye 4nU/dHjTT8OihpwvQrhEtMneNEiZ+BNLjGgwDF8bbU5AlQSpb5dFH+S+tGhJWxEd 09C7D7ETFzkUPu+ulcxdPM6IPkbHKnKQJvvMryt5zHDElweOqa6pnv6x+SY/Zcdq WZ5zQ6xEZciUqpzHIZhff0Z8uzURLdEIZf8ZeKUw== 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 4cf24gngyv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 Feb 2026 12:04:30 +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 61Q9mwCi013406; Thu, 26 Feb 2026 12:04:29 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4cfqdyb7y5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 Feb 2026 12:04:28 +0000 Received: from smtpav06.fra02v.mail.ibm.com (smtpav06.fra02v.mail.ibm.com [10.20.54.105]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 61QC4OrB52101570 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 Feb 2026 12:04:24 GMT Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C3E8420049; Thu, 26 Feb 2026 12:04:24 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 58AF220040; Thu, 26 Feb 2026 12:04:24 +0000 (GMT) Received: from osiris (unknown [9.52.214.206]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 26 Feb 2026 12:04:24 +0000 (GMT) Date: Thu, 26 Feb 2026 13:04:22 +0100 From: Heiko Carstens To: Mathieu Desnoyers Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Paul E. McKenney" , Steven Rostedt , Masami Hiramatsu , Dennis Zhou , Tejun Heo , Christoph Lameter , Martin Liu , David Rientjes , christian.koenig@amd.com, Shakeel Butt , SeongJae Park , Michal Hocko , Johannes Weiner , Sweet Tea Dorminy , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Christian Brauner , Wei Yang , David Hildenbrand , Miaohe Lin , Al Viro , linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, Yu Zhao , Roman Gushchin , Mateusz Guzik , Matthew Wilcox , Baolin Wang , Aboorva Devarajan , Vasily Gorbik , linux-s390@vger.kernel.org Subject: Re: [PATCH v17 0/3] Improve proc RSS accuracy Message-ID: <20260226120422.8101Cc2-hca@linux.ibm.com> References: <20260217161006.1105611-1-mathieu.desnoyers@efficios.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260217161006.1105611-1-mathieu.desnoyers@efficios.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=TNRIilla c=1 sm=1 tr=0 ts=69a036ce cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=kj9zAlcOel0A:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=VwQbUJbxAAAA:8 a=7d_E57ReAAAA:8 a=Z4Rwk6OoAAAA:8 a=Z2se5BRXh4BkGdnmWtwA:9 a=CjuIK1q_8ugA:10 a=jhqOcbufqs7Y1TYCrUUU:22 a=HkZW87K1Qel5hWWM3VKY:22 X-Proofpoint-GUID: tD1VGSP6HieBCF5wEAHv0bKZIDdXK7aS X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI2MDEwNSBTYWx0ZWRfXxnBFMIMGvx93 NdpWAzHcd9kNIM7tpzuPDi3BSVm5oNJyX6k7U0zZdM32iWRNeKiIIDNyDwhW1ie1R6T7aYFi1O/ 4fTTnuaMtg+xKW1e1SAZWgaAArbF6sYmYRLl0D+MSZtAg1edED7r4cnXS7CPaeMF9mzXf9faZ1z qpQdHAJooVMDsMDGOkFzgtGitkCuFBpyeTRc6t74i/nwBL9/4KpF6bQ7on4XWzxPvWRijLBIcOv ujVTdWIdcqGk/3fdev5KpkuWBOoop05s2VqEGRalxYfMIHqrcIup+G8zDyxRelcgxsGbr8FC8Cj X9bx/fneQd6kt42vykx7myCLplIrWu/25T3vAdeEcbCbhHiXItBLsdtoAwUQ0/+Im47jQZbTkhT wN+y90PoLt8pSiXfN5aITpdmy7OKN6jXjHJTn2mvgLfS6k6L2dfKdg7fXZsMgJL27bQk0EH3CkN 9JG/g+VOAbbevvP5dag== X-Proofpoint-ORIG-GUID: 8HrdOn9qyY5RT1ScPmZUbcFIKf-LaGiO 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_04,2026-02-25_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 adultscore=0 priorityscore=1501 impostorscore=0 spamscore=0 clxscore=1011 bulkscore=0 lowpriorityscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602260105 On Tue, Feb 17, 2026 at 11:10:03AM -0500, Mathieu Desnoyers wrote: > This series introduces the hierarchical tree counter (hpcc) to increase > accuracy of approximated RSS counters exposed through proc interfaces. > > With a test program hopping across CPUs doing frequent mmap/munmap > operations, the upstream implementation approximation reaches a 1GB > delta from the precise value after a few minutes, compared to a 80MB > delta with the hierarchical counter. The hierarchical counter provides a > guaranteed maximum approximation inaccuracy of 192MB on that hardware > topology. > > This series is based on > commit 0f2acd3148e0 Merge tag 'm68knommu-for-v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu > > The main changes since v16: > - Dropped OOM killer 2-pass task selection algorithm. > - Introduce Kunit tests. > - Only perform atomic increments of intermediate tree nodes when > bits which are significant for carry propagation are being changed. This seems to cause crashes with linux-next on s390, at least I could bisect it to the last patch of this series. Reverting the last one, makes the crashes go away: 0acac6604c1cfd7a1762901f0a4abe87cf3a8619 is the first bad commit commit 0acac6604c1cfd7a1762901f0a4abe87cf3a8619 (HEAD) Author: Mathieu Desnoyers AuthorDate: Tue Feb 17 11:10:06 2026 -0500 Commit: Andrew Morton CommitDate: Tue Feb 24 11:15:15 2026 -0800 mm: improve RSS counter approximation accuracy for proc interfaces Unable to handle kernel pointer dereference in virtual kernel address space Failing address: 766d615f72615000 TEID: 766d615f72615803 ESOP-2 FSI Fault in home space mode while using kernel ASCE. AS:000000025dc04007 R3:0000000000000024 Oops: 0038 ilc:2 [#1]SMP Modules linked in: CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-20260224.rc1.git266.3ef088b0c577.300.fc43.s390x+next #1 PREEMPTLAZY Hardware name: IBM 3931 A01 703 (z/VM 7.4.0) Krnl PSW : 0704c00180000000 00000216ef164cde (kernfs_name_hash+0x1e/0xb0) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 0000000000000000 766d615f72615f65 0000000000000000 766d615f72615f65 0000000000000000 0000000000000000 0000000000000000 766d615f72615f65 0000000081212440 0000000000000000 0000000000000000 0000000080a00000 00000216efcb5390 00000216ef16530c 00000196eeb07ae0 Krnl Code: 00000216ef164cd2: a7190000 lghi %r1,0 00000216ef164cd6: b9040042 lgr %r4,%r2 *00000216ef164cda: a7090000 lghi %r0,0 >00000216ef164cde: b25e0014 srst %r1,%r4 00000216ef164ce2: a714fffe brc 1,00000216ef164cde 00000216ef164ce6: b9e92051 sgrk %r5,%r1,%r2 00000216ef164cea: ec1200208076 crj %r1,%r2,8,00000216ef164d2a 00000216ef164cf0: b9160005 llgfr %r0,%r5 Call Trace: [<00000216ef164cde>] kernfs_name_hash+0x1e/0xb0 [<00000216ef167d32>] kernfs_remove_by_name_ns+0x72/0x120 [<00000216ef16bbfa>] remove_files+0x4a/0x90 [<00000216ef16bf96>] create_files+0x276/0x2b0 [<00000216ef16c15a>] internal_create_group+0x18a/0x320 [<00000216f09b61c6>] swap_init+0x5e/0xa0 [<00000216eec7fb00>] do_one_initcall+0x40/0x270 [<00000216f0990a40>] kernel_init_freeable+0x2b0/0x330 [<00000216efb5160e>] kernel_init+0x2e/0x180 [<00000216eec81ffc>] __ret_from_fork+0x3c/0x240 [<00000216efb5e052>] ret_from_fork+0xa/0x30 Last Breaking-Event-Address: [<00000216ef165306>] kernfs_find_ns+0x76/0x140 Kernel panic - not syncing: Fatal exception: panic_on_oops