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Thu, 10 Apr 2025 15:45:09 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 348C520043; Thu, 10 Apr 2025 15:45:09 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E51B920040; Thu, 10 Apr 2025 15:45:05 +0000 (GMT) Received: from li-3c92a0cc-27cf-11b2-a85c-b804d9ca68fa.ibm.com (unknown [9.39.22.39]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 10 Apr 2025 15:45:05 +0000 (GMT) Date: Thu, 10 Apr 2025 21:15:03 +0530 From: Aditya Gupta To: Gavin Shan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, donettom@linux.ibm.com, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, akpm@linux-foundation.org, shan.gavin@gmail.com Subject: Re: [PATCH] drivers/base/memory: Avoid overhead from for_each_present_section_nr() Message-ID: References: <20250410125110.1232329-1-gshan@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250410125110.1232329-1-gshan@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: uW4bl6wW8n_-J2BrYXkOUvRPlo8dosy3 X-Proofpoint-ORIG-GUID: FQ-8hx6H6kTI4vK32YKxEEy4k9s9YRoi X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1095,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-04-10_04,2025-04-10_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 mlxlogscore=629 phishscore=0 mlxscore=0 priorityscore=1501 suspectscore=0 adultscore=0 bulkscore=0 spamscore=0 clxscore=1015 impostorscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2504100112 X-Rspamd-Queue-Id: 9E5B0160008 X-Stat-Signature: wftug3agb7sozukp18cb7zdimzr1zzwm X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1744299921-459251 X-HE-Meta: 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 EL40Lhqg qHwiTGJQrbrdQ8upGMgi+zrWatd4HXQwx0yH2kuE6I0azJwkTjngLzixcgosb41IxatLjVZUrlxSVDS9kV0Y5EyxQ9XGW+a7M1yT+DVdkfL94kdytrshp77nwanKTCn2GB0MBC9Ht4HYAcD/jNWRuFaotJKVhmVe3hsbPSU5gNgNJsXh3SLea49r6XD+iSwruvPypZIREeQZO9OIYIvgeCMvGQChxGO5u18fUe0WPqRfD6L/vDRo1sa5A1YdvjGlDVbG7FdjNRXOsnqelH9ISt4H9YBAREU3spYxBXlg0q5WSs1iZcj+S40OA3PzlvG1jJDglEbRTzLxtVR1DlkRs76D12qbYDUQpc/Cd9XafcOlLKHJb4YO3QmBI3knQ2ZQ0LpkeqPfLWSxkkIk74FRqCrqku8MwBA7sN0+P X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 25/04/10 10:51PM, Gavin Shan wrote: > for_each_present_section_nr() was introduced to add_boot_memory_block() > by commit 61659efdb35c ("drivers/base/memory: improve add_boot_memory_block()"). > It causes unnecessary overhead when the present sections are really > sparse. next_present_section_nr() called by the macro to find the next > present section, which is far away from the spanning sections in the > specified block. Too much time consumed by next_present_section_nr() > in this case, which can lead to softlockup as observed by Aditya Gupta > on IBM Power10 machine. > > watchdog: BUG: soft lockup - CPU#248 stuck for 22s! [swapper/248:1] > Modules linked in: > CPU: 248 UID: 0 PID: 1 Comm: swapper/248 Not tainted 6.15.0-rc1-next-20250408 #1 VOLUNTARY > Hardware name: 9105-22A POWER10 (raw) 0x800200 opal:v7.1-107-gfda75d121942 PowerNV > NIP: c00000000209218c LR: c000000002092204 CTR: 0000000000000000 > REGS: c00040000418fa30 TRAP: 0900 Not tainted (6.15.0-rc1-next-20250408) > MSR: 9000000002009033 CR: 28000428 XER: 00000000 > CFAR: 0000000000000000 IRQMASK: 0 > GPR00: c000000002092204 c00040000418fcd0 c000000001b08100 0000000000000040 > GPR04: 0000000000013e00 c000c03ffebabb00 0000000000c03fff c000400fff587f80 > GPR08: 0000000000000000 00000000001196f7 0000000000000000 0000000028000428 > GPR12: 0000000000000000 c000000002e80000 c00000000001007c 0000000000000000 > GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR28: c000000002df7f70 0000000000013dc0 c0000000011dd898 0000000008000000 > NIP [c00000000209218c] memory_dev_init+0x114/0x1e0 > LR [c000000002092204] memory_dev_init+0x18c/0x1e0 > Call Trace: > [c00040000418fcd0] [c000000002092204] memory_dev_init+0x18c/0x1e0 (unreliable) > [c00040000418fd50] [c000000002091348] driver_init+0x78/0xa4 > [c00040000418fd70] [c0000000020063ac] kernel_init_freeable+0x22c/0x370 > [c00040000418fde0] [c0000000000100a8] kernel_init+0x34/0x25c > [c00040000418fe50] [c00000000000cd94] ret_from_kernel_user_thread+0x14/0x1c > > Avoid the overhead by folding for_each_present_section_nr() to the outer > loop. add_boot_memory_block() is dropped after that. > > Fixes: 61659efdb35c ("drivers/base/memory: improve add_boot_memory_block()") > Closes: https://lore.kernel.org/linux-mm/20250409180344.477916-1-adityag@linux.ibm.com > Reported-by: Aditya Gupta > Signed-off-by: Gavin Shan > --- > drivers/base/memory.c | 41 +++++++++++++++++------------------------ > 1 file changed, 17 insertions(+), 24 deletions(-) Thanks for the fix, Gavin. Tested on PowerNV Power10 hardware on which the issue was originally seen, the patch fixes the softlockup issue. Hence, Tested-by: Aditya Gupta Thanks, - Aditya G