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=-9.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 6BD19C433E2 for ; Wed, 16 Sep 2020 07:47:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 096DA2080C for ; Wed, 16 Sep 2020 07:47:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 096DA2080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 72D666B005A; Wed, 16 Sep 2020 03:47:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6DE736B005C; Wed, 16 Sep 2020 03:47:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5F4F66B005D; Wed, 16 Sep 2020 03:47:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0082.hostedemail.com [216.40.44.82]) by kanga.kvack.org (Postfix) with ESMTP id 45D3A6B005A for ; Wed, 16 Sep 2020 03:47:28 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 03BAE2C1F for ; Wed, 16 Sep 2020 07:47:28 +0000 (UTC) X-FDA: 77268144576.29.box11_3c115d327118 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin29.hostedemail.com (Postfix) with ESMTP id AF834180868DE for ; Wed, 16 Sep 2020 07:47:27 +0000 (UTC) X-HE-Tag: box11_3c115d327118 X-Filterd-Recvd-Size: 5632 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Wed, 16 Sep 2020 07:47:27 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C30FDB460; Wed, 16 Sep 2020 07:47:40 +0000 (UTC) Date: Wed, 16 Sep 2020 09:47:15 +0200 From: Michal Hocko To: Vijay Balakrishna Cc: Andrew Morton , "Kirill A. Shutemov" , Oleg Nesterov , Song Liu , Andrea Arcangeli , Pavel Tatashin , Allen Pais , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [v2 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged Message-ID: <20200916074715.GD18998@dhcp22.suse.cz> References: <1600204258-13683-1-git-send-email-vijayb@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1600204258-13683-1-git-send-email-vijayb@linux.microsoft.com> X-Rspamd-Queue-Id: AF834180868DE X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 15-09-20 14:10:57, Vijay Balakrishna wrote: > When memory is hotplug added or removed the min_free_kbytes must be > recalculated based on what is expected by khugepaged. Currently > after hotplug, min_free_kbytes will be set to a lower default and higher > default set when THP enabled is lost. This leaves the system with small > min_free_kbytes which isn't suitable for systems especially with network > intensive loads. Typical failure symptoms include HW WATCHDOG reset, > soft lockup hang notices, NETDEVICE WATCHDOG timeouts, and OOM process > kills. This changelog still doesn't explain the underlying problem IMO. It sounds it is papering over some other problem. I do agree that the current behavior is non intuitive and surprising. Justifying the change by that inconsistency is likely much better than arguing with soft lockups and OOMs which shouldn't be a result of this inconsistency. > Fixes: f000565adb77 ("thp: set recommended min free kbytes") > > Signed-off-by: Vijay Balakrishna > Cc: stable@vger.kernel.org > Reviewed-by: Pavel Tatashin > --- > include/linux/khugepaged.h | 5 +++++ > mm/khugepaged.c | 13 +++++++++++-- > mm/memory_hotplug.c | 3 +++ > 3 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > index bc45ea1efbf7..c941b7377321 100644 > --- a/include/linux/khugepaged.h > +++ b/include/linux/khugepaged.h > @@ -15,6 +15,7 @@ extern int __khugepaged_enter(struct mm_struct *mm); > extern void __khugepaged_exit(struct mm_struct *mm); > extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, > unsigned long vm_flags); > +extern void khugepaged_min_free_kbytes_update(void); > #ifdef CONFIG_SHMEM > extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr); > #else > @@ -85,6 +86,10 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm, > unsigned long addr) > { > } > + > +static inline void khugepaged_min_free_kbytes_update(void) > +{ > +} > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > #endif /* _LINUX_KHUGEPAGED_H */ > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index cfa0dba5fd3b..4f7107476a6f 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -56,6 +56,9 @@ enum scan_result { > #define CREATE_TRACE_POINTS > #include > > +static struct task_struct *khugepaged_thread __read_mostly; > +static DEFINE_MUTEX(khugepaged_mutex); > + > /* default scan 8*512 pte (or vmas) every 30 second */ > static unsigned int khugepaged_pages_to_scan __read_mostly; > static unsigned int khugepaged_pages_collapsed; > @@ -2292,8 +2295,6 @@ static void set_recommended_min_free_kbytes(void) > > int start_stop_khugepaged(void) > { > - static struct task_struct *khugepaged_thread __read_mostly; > - static DEFINE_MUTEX(khugepaged_mutex); > int err = 0; > > mutex_lock(&khugepaged_mutex); > @@ -2320,3 +2321,11 @@ int start_stop_khugepaged(void) > mutex_unlock(&khugepaged_mutex); > return err; > } > + > +void khugepaged_min_free_kbytes_update(void) > +{ > + mutex_lock(&khugepaged_mutex); > + if (khugepaged_enabled() && khugepaged_thread) > + set_recommended_min_free_kbytes(); > + mutex_unlock(&khugepaged_mutex); > +} > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index e9d5ab5d3ca0..3e19272c1fad 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -36,6 +36,7 @@ > #include > #include > #include > +#include > > #include > > @@ -857,6 +858,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, > zone_pcp_update(zone); > > init_per_zone_wmark_min(); > + khugepaged_min_free_kbytes_update(); > > kswapd_run(nid); > kcompactd_run(nid); > @@ -1600,6 +1602,7 @@ static int __ref __offline_pages(unsigned long start_pfn, > pgdat_resize_unlock(zone->zone_pgdat, &flags); > > init_per_zone_wmark_min(); > + khugepaged_min_free_kbytes_update(); > > if (!populated_zone(zone)) { > zone_pcp_reset(zone); > -- > 2.28.0 -- Michal Hocko SUSE Labs