From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 20B3A8E0001 for ; Thu, 10 Jan 2019 18:31:50 -0500 (EST) Received: by mail-pf1-f197.google.com with SMTP id q64so8875098pfa.18 for ; Thu, 10 Jan 2019 15:31:50 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id f81si19831324pfh.33.2019.01.10.15.31.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Jan 2019 15:31:48 -0800 (PST) Date: Thu, 10 Jan 2019 15:31:47 -0800 From: Andrew Morton 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 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. */