From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAEE9C433DB for ; Wed, 10 Mar 2021 09:15:17 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C8BAF64F67 for ; Wed, 10 Mar 2021 09:15:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C8BAF64F67 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4DwRHk6r7Gz3d47 for ; Wed, 10 Mar 2021 20:15:14 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4DwRHK62fPz30Ng for ; Wed, 10 Mar 2021 20:14:50 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4DwRHB5pJwz9tyyl; Wed, 10 Mar 2021 10:14:46 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 0ls_2FiszXcP; Wed, 10 Mar 2021 10:14:46 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4DwRHB4KSkz9tyyk; Wed, 10 Mar 2021 10:14:46 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 97B6A8B786; Wed, 10 Mar 2021 10:14:47 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id FDKXEONqcFgv; Wed, 10 Mar 2021 10:14:47 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 140C58B77E; Wed, 10 Mar 2021 10:14:47 +0100 (CET) Subject: Re: [PATCH] powerpc/mm: Add cond_resched() while removing hpte mappings To: Vaibhav Jain , linuxppc-dev@lists.ozlabs.org References: <20210310075938.361656-1-vaibhav@linux.ibm.com> From: Christophe Leroy Message-ID: <6acf3ba8-296d-a8f7-4242-eeb5f05edf40@csgroup.eu> Date: Wed, 10 Mar 2021 10:14:42 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210310075938.361656-1-vaibhav@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Aneesh Kumar K . V" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 10/03/2021 à 08:59, Vaibhav Jain a écrit : > While removing large number of mappings from hash page tables for > large memory systems as soft-lockup is reported because of the time > spent inside htap_remove_mapping() like one below: > > watchdog: BUG: soft lockup - CPU#8 stuck for 23s! > > NIP plpar_hcall+0x38/0x58 > LR pSeries_lpar_hpte_invalidate+0x68/0xb0 > Call Trace: > 0x1fffffffffff000 (unreliable) > pSeries_lpar_hpte_removebolted+0x9c/0x230 > hash__remove_section_mapping+0xec/0x1c0 > remove_section_mapping+0x28/0x3c > arch_remove_memory+0xfc/0x150 > devm_memremap_pages_release+0x180/0x2f0 > devm_action_release+0x30/0x50 > release_nodes+0x28c/0x300 > device_release_driver_internal+0x16c/0x280 > unbind_store+0x124/0x170 > drv_attr_store+0x44/0x60 > sysfs_kf_write+0x64/0x90 > kernfs_fop_write+0x1b0/0x290 > __vfs_write+0x3c/0x70 > vfs_write+0xd4/0x270 > ksys_write+0xdc/0x130 > system_call+0x5c/0x70 > > Fix this by adding a cond_resched() to the loop in > htap_remove_mapping() that issues hcall to remove hpte mapping. This > should prevent the soft-lockup from being reported. Isn't it overkill to call is at each iteration ? Looking at a few other places, there is some mitigation. For instance fadump_free_reserved_memory() does it based on elapsed time. Another exemple is drmem_lmb_next() doing it every 16 iteration. > > Suggested-by: Aneesh Kumar K.V > Signed-off-by: Vaibhav Jain > --- > arch/powerpc/mm/book3s64/hash_utils.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c > index 581b20a2feaf..ea3945c70b18 100644 > --- a/arch/powerpc/mm/book3s64/hash_utils.c > +++ b/arch/powerpc/mm/book3s64/hash_utils.c > @@ -359,6 +359,8 @@ int htab_remove_mapping(unsigned long vstart, unsigned long vend, > } > if (rc < 0) > return rc; > + > + cond_resched(); > } > > return ret; > Christophe