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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 C5C1CC43387 for ; Thu, 10 Jan 2019 23:31:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 946EA214C6 for ; Thu, 10 Jan 2019 23:31:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730236AbfAJXbt (ORCPT ); Thu, 10 Jan 2019 18:31:49 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:33362 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727846AbfAJXbt (ORCPT ); Thu, 10 Jan 2019 18:31:49 -0500 Received: from localhost.localdomain (c-24-6-170-16.hsd1.ca.comcast.net [24.6.170.16]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 2598E1217; Thu, 10 Jan 2019 23:31:48 +0000 (UTC) Date: Thu, 10 Jan 2019 15:31:47 -0800 From: Andrew Morton To: Yang Shi Cc: ying.huang@intel.com, tim.c.chen@intel.com, minchan@kernel.org, daniel.m.jordan@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v5 PATCH 1/2] mm: swap: check if swap backing device is congested or not Message-Id: <20190110153147.1baf4c88bf0dd3b8a78aad08@linux-foundation.org> In-Reply-To: <1546543673-108536-1-git-send-email-yang.shi@linux.alibaba.com> References: <1546543673-108536-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 4 Jan 2019 03:27:52 +0800 Yang Shi wrote: > Swap readahead would read in a few pages regardless if the underlying > device is busy or not. It may incur long waiting time if the device is > congested, and it may also exacerbate the congestion. > > Use inode_read_congested() to check if the underlying device is busy or > not like what file page readahead does. Get inode from swap_info_struct. > Although we can add inode information in swap_address_space > (address_space->host), it may lead some unexpected side effect, i.e. > it may break mapping_cap_account_dirty(). Using inode from > swap_info_struct seems simple and good enough. > > ... > > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -538,11 +538,18 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, > bool do_poll = true, page_allocated; > struct vm_area_struct *vma = vmf->vma; > unsigned long addr = vmf->address; > + struct inode *inode = NULL; > > mask = swapin_nr_pages(offset) - 1; > if (!mask) > goto skip; > > + if (si->flags & (SWP_BLKDEV | SWP_FS)) { I re-read your discussion with Tim and I must say the reasoning behind this test remain foggy. What goes wrong if we just remove it? What is the status of shmem swap readahead? Can we at least get a comment in here which explains the reasoning? Thanks. > + inode = si->swap_file->f_mapping->host; > + if (inode_read_congested(inode)) > + goto skip; > + } > + > do_poll = false; > /* Read a page_cluster sized and aligned cluster around offset. */