From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752916AbdBPIV2 (ORCPT ); Thu, 16 Feb 2017 03:21:28 -0500 Received: from out0-149.mail.aliyun.com ([140.205.0.149]:44912 "EHLO out0-149.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbdBPIV1 (ORCPT ); Thu, 16 Feb 2017 03:21:27 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R461e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03312;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---.7dhvnAE_1487233264; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "'Mel Gorman'" Cc: "'Andrew Morton'" , "'Shantanu Goel'" , "'Chris Mason'" , "'Johannes Weiner'" , "'Vlastimil Babka'" , "'LKML'" , "'Linux-MM'" References: <20170215092247.15989-1-mgorman@techsingularity.net> <20170215092247.15989-4-mgorman@techsingularity.net> <001501d2881d$242aa790$6c7ff6b0$@alibaba-inc.com> <20170216081039.ukbxl2b4khnwwbic@techsingularity.net> In-Reply-To: <20170216081039.ukbxl2b4khnwwbic@techsingularity.net> Subject: Re: [PATCH 3/3] mm, vmscan: Prevent kswapd sleeping prematurely due to mismatched classzone_idx Date: Thu, 16 Feb 2017 16:21:04 +0800 Message-ID: <001f01d2882d$9dd14850$d973d8f0$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQKB+Y4QbCcdRwF90qCW6BKDtoYfwAHHz9YmApgb8HQB8Bf2XZ/Z5k7A Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On February 16, 2017 4:11 PM Mel Gorman wrote: > On Thu, Feb 16, 2017 at 02:23:08PM +0800, Hillf Danton wrote: > > On February 15, 2017 5:23 PM Mel Gorman wrote: > > > */ > > > static int kswapd(void *p) > > > { > > > - unsigned int alloc_order, reclaim_order, classzone_idx; > > > + unsigned int alloc_order, reclaim_order; > > > + unsigned int classzone_idx = MAX_NR_ZONES - 1; > > > pg_data_t *pgdat = (pg_data_t*)p; > > > struct task_struct *tsk = current; > > > > > > @@ -3447,20 +3466,23 @@ static int kswapd(void *p) > > > tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; > > > set_freezable(); > > > > > > - pgdat->kswapd_order = alloc_order = reclaim_order = 0; > > > - pgdat->kswapd_classzone_idx = classzone_idx = 0; > > > + pgdat->kswapd_order = 0; > > > + pgdat->kswapd_classzone_idx = MAX_NR_ZONES; > > > for ( ; ; ) { > > > bool ret; > > > > > > + alloc_order = reclaim_order = pgdat->kswapd_order; > > > + classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx); > > > + > > > kswapd_try_sleep: > > > kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order, > > > classzone_idx); > > > > > > /* Read the new order and classzone_idx */ > > > alloc_order = reclaim_order = pgdat->kswapd_order; > > > - classzone_idx = pgdat->kswapd_classzone_idx; > > > + classzone_idx = kswapd_classzone_idx(pgdat, 0); > > > pgdat->kswapd_order = 0; > > > - pgdat->kswapd_classzone_idx = 0; > > > + pgdat->kswapd_classzone_idx = MAX_NR_ZONES; > > > > > > ret = try_to_freeze(); > > > if (kthread_should_stop()) > > > @@ -3486,9 +3508,6 @@ static int kswapd(void *p) > > > reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx); > > > if (reclaim_order < alloc_order) > > > goto kswapd_try_sleep; > > > > If we fail order-5 request, can we then give up order-5, and > > try order-3 if requested, after napping? > > > > That has no bearing upon this patch. At this point, kswapd has stopped > reclaiming at the requested order and is preparing to sleep. If there is > a parallel request for order-3 while it's sleeping, it'll wake and start > reclaiming at order-3 as requested. > Right, but the order-3 request can also come up while kswapd is active and gives up order-5. thanks Hillf