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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F28AEC47089 for ; Tue, 6 Dec 2022 01:40:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233302AbiLFBkM (ORCPT ); Mon, 5 Dec 2022 20:40:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232343AbiLFBkH (ORCPT ); Mon, 5 Dec 2022 20:40:07 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9CE2B58 for ; Mon, 5 Dec 2022 17:40:05 -0800 (PST) Received: from dggpemm500001.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NR30C2fBTzqSh2; Tue, 6 Dec 2022 09:35:55 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 6 Dec 2022 09:40:03 +0800 Message-ID: <34a694c8-eb12-757a-05e3-f87f3ba1347a@huawei.com> Date: Tue, 6 Dec 2022 09:40:02 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] mm: add cond_resched() in swapin_walk_pmd_entry() Content-Language: en-US To: Andrew Morton CC: , , References: <20221205140327.72304-1-wangkefeng.wang@huawei.com> <20221205130359.2c81c5df0fb777cf55495a02@linux-foundation.org> From: Kefeng Wang In-Reply-To: <20221205130359.2c81c5df0fb777cf55495a02@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/12/6 5:03, Andrew Morton wrote: > On Mon, 5 Dec 2022 22:03:27 +0800 Kefeng Wang wrote: > >> When handle MADV_WILLNEED in madvise(), the soflockup may be occurred >> in swapin_walk_pmd_entry() if swapin lots of memory on slow device, >> add a cond_resched() into it to avoid the possible softlockup. >> >> ... >> >> --- a/mm/madvise.c >> +++ b/mm/madvise.c >> @@ -226,6 +226,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, >> put_page(page); >> } >> swap_read_unplug(splug); >> + cond_resched(); >> >> return 0; >> } > I wonder if this would be better in walk_pmd_range(), to address other > very large walk attempts. mm/madvise.c:287:       walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma); mm/madvise.c:514:       walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private); mm/madvise.c:762:       walk_page_range(vma->vm_mm, range.start, range.end, mm/madvise.c-763-                       &madvise_free_walk_ops, &tlb); The cold_walk_ops and madvise_free_walk_ops are already with cond_resched() in theirs pmd_entry walk, maybe there's no need for a precautionary increase a cond_resched() for now > > .