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Thu, 10 Apr 2025 12:51:22 +0000 (UTC) Received: from gshan-thinkpadx1nanogen2.remote.csb (unknown [10.64.136.115]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 51F6119560AD; Thu, 10 Apr 2025 12:51:16 +0000 (UTC) From: Gavin Shan To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, adityag@linux.ibm.com, donettom@linux.ibm.com, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, shan.gavin@gmail.com Subject: [PATCH] drivers/base/memory: Avoid overhead from for_each_present_section_nr() Date: Thu, 10 Apr 2025 22:51:10 +1000 Message-ID: <20250410125110.1232329-1-gshan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 59BE780009 X-Stat-Signature: 7c47x8fu534zksud3j5fcrbk6mchypwr X-HE-Tag: 1744289488-487937 X-HE-Meta: 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 uLBgaKcz 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 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: 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 Acked-by: Oscar Salvador Acked-by: David Hildenbrand Tested-by: Aditya Gupta --- drivers/base/memory.c | 41 +++++++++++++++++------------------------ 1 file changed, 17 insertions(+), 24 deletions(-) diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 8f3a41d9bfaa..19469e7f88c2 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -816,21 +816,6 @@ static int add_memory_block(unsigned long block_id, unsigned long state, return 0; } -static int __init add_boot_memory_block(unsigned long base_section_nr) -{ - unsigned long nr; - - for_each_present_section_nr(base_section_nr, nr) { - if (nr >= (base_section_nr + sections_per_block)) - break; - - return add_memory_block(memory_block_id(base_section_nr), - MEM_ONLINE, NULL, NULL); - } - - return 0; -} - static int add_hotplug_memory_block(unsigned long block_id, struct vmem_altmap *altmap, struct memory_group *group) @@ -957,7 +942,7 @@ static const struct attribute_group *memory_root_attr_groups[] = { void __init memory_dev_init(void) { int ret; - unsigned long block_sz, nr; + unsigned long block_sz, block_id, nr; /* Validate the configured memory block size */ block_sz = memory_block_size_bytes(); @@ -970,15 +955,23 @@ void __init memory_dev_init(void) panic("%s() failed to register subsystem: %d\n", __func__, ret); /* - * Create entries for memory sections that were found - * during boot and have been initialized + * Create entries for memory sections that were found during boot + * and have been initialized. Use @block_id to track the last + * handled block and initialize it to an invalid value (ULONG_MAX) + * to bypass the block ID matching check for the first present + * block so that it can be covered. */ - for (nr = 0; nr <= __highest_present_section_nr; - nr += sections_per_block) { - ret = add_boot_memory_block(nr); - if (ret) - panic("%s() failed to add memory block: %d\n", __func__, - ret); + block_id = ULONG_MAX; + for_each_present_section_nr(0, nr) { + if (block_id != ULONG_MAX && memory_block_id(nr) == block_id) + continue; + + block_id = memory_block_id(nr); + ret = add_memory_block(block_id, MEM_ONLINE, NULL, NULL); + if (ret) { + panic("%s() failed to add memory block: %d\n", + __func__, ret); + } } }