From patchwork Thu Oct 31 23:46:08 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Chinner X-Patchwork-Id: 11222159 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 98C10912 for ; Thu, 31 Oct 2019 23:47:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 80F6820873 for ; Thu, 31 Oct 2019 23:47:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729559AbfJaXrl (ORCPT ); Thu, 31 Oct 2019 19:47:41 -0400 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:40131 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728696AbfJaXqc (ORCPT ); Thu, 31 Oct 2019 19:46:32 -0400 Received: from dread.disaster.area (pa49-180-67-183.pa.nsw.optusnet.com.au [49.180.67.183]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 61A077EA3C0; Fri, 1 Nov 2019 10:46:26 +1100 (AEDT) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92.3) (envelope-from ) id 1iQK8x-0007CU-Jz; Fri, 01 Nov 2019 10:46:19 +1100 Received: from dave by discord.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1iQK8x-000421-Hp; Fri, 01 Nov 2019 10:46:19 +1100 From: Dave Chinner To: linux-xfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 18/28] xfs: don't block kswapd in inode reclaim Date: Fri, 1 Nov 2019 10:46:08 +1100 Message-Id: <20191031234618.15403-19-david@fromorbit.com> X-Mailer: git-send-email 2.24.0.rc0 In-Reply-To: <20191031234618.15403-1-david@fromorbit.com> References: <20191031234618.15403-1-david@fromorbit.com> MIME-Version: 1.0 X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=D+Q3ErZj c=1 sm=1 tr=0 a=3wLbm4YUAFX2xaPZIabsgw==:117 a=3wLbm4YUAFX2xaPZIabsgw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=MeAgGD-zjQ4A:10 a=20KFwNOVAAAA:8 a=x2yLRZ3W9cWBXR4-ZBgA:9 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Dave Chinner We have a number of reasons for blocking kswapd in XFS inode reclaim, mainly all to do with the fact that memory reclaim has no feedback mechanisms to throttle on dirty slab objects that need IO to reclaim. As a result, we currently throttle inode reclaim by issuing IO in the reclaim context. The unfortunate side effect of this is that it can cause long tail latencies in reclaim and for some workloads this can be a problem. Now that the shrinkers finally have a method of telling kswapd to back off, we can start the process of making inode reclaim in XFS non-blocking. The first thing we need to do is not block kswapd, but so that doesn't cause immediate serious problems, make sure inode writeback is always underway when kswapd is running. As we don't block kswapd now, we don't have to worry about reclaim scans taking long delays due to IO being issued and waited for. Hence while direct reclaim gets delayed by IO, kswapd will not and so it will keep pushing the AIL to clean inodes. Hence direct reclaim doesn't need to push the AIL anymore as kswapd will do it reliably now. Signed-off-by: Dave Chinner Reviewed-by: Brian Foster --- fs/xfs/xfs_icache.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c index 944add5ff8e0..edcc3f6bb3bf 100644 --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -1378,11 +1378,22 @@ xfs_reclaim_inodes_nr( struct xfs_mount *mp, int nr_to_scan) { - /* kick background reclaimer and push the AIL */ + int sync_mode = SYNC_TRYLOCK; + + /* kick background reclaimer */ xfs_reclaim_work_queue(mp); - xfs_ail_push_all(mp->m_ail); - return xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan); + /* + * For kswapd, we kick background inode writeback. For direct + * reclaim, we issue and wait on inode writeback to throttle + * reclaim rates and avoid shouty OOM-death. + */ + if (current_is_kswapd()) + xfs_ail_push_all(mp->m_ail); + else + sync_mode |= SYNC_WAIT; + + return xfs_reclaim_inodes_ag(mp, sync_mode, &nr_to_scan); } /*