From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) by kanga.kvack.org (Postfix) with ESMTP id 8CC6D8E0001 for ; Fri, 21 Dec 2018 20:11:54 -0500 (EST) Received: by mail-pl1-f198.google.com with SMTP id g12so5297789pll.22 for ; Fri, 21 Dec 2018 17:11:54 -0800 (PST) Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com. [115.124.30.130]) by mx.google.com with ESMTPS id x191si22955144pfd.220.2018.12.21.17.11.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Dec 2018 17:11:53 -0800 (PST) Subject: Re: [v3 PATCH 1/2] mm: swap: check if swap backing device is congested or not References: <1545428420-126557-1-git-send-email-yang.shi@linux.alibaba.com> From: Yang Shi Message-ID: Date: Fri, 21 Dec 2018 17:09:07 -0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: Tim Chen , ying.huang@intel.com, tim.c.chen@intel.com, minchan@kernel.org, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 12/21/18 2:42 PM, Tim Chen wrote: > On 12/21/18 1:40 PM, 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. >> >> Just does the check in vma_cluster_readahead() since >> swap_vma_readahead() is just used for non-rotational device which >> much less likely has congestion than traditional HDD. >> >> Although swap slots may be consecutive on swap partition, it still may be >> fragmented on swap file. This check would help to reduce excessive stall >> for such case. >> >> Cc: Huang Ying >> Cc: Tim Chen >> Cc: Minchan Kim >> Signed-off-by: Yang Shi >> --- >> v3: Move inode deference under swap device type check per Tim Chen >> v2: Check the swap device type per Tim Chen >> >> mm/swap_state.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/mm/swap_state.c b/mm/swap_state.c >> index fd2f21e..78d500e 100644 >> --- 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)) { >> + 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. */ >> start_offset = offset & ~mask; >> > Acked-by: Tim Chen Thanks. Happy holiday.