From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 191318E0038 for ; Wed, 9 Jan 2019 03:40:35 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id b7so2637212eda.10 for ; Wed, 09 Jan 2019 00:40:35 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id g4si1037863edp.176.2019.01.09.00.40.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Jan 2019 00:40:33 -0800 (PST) Date: Wed, 9 Jan 2019 09:40:31 +0100 From: Michal Hocko Subject: Re: [PATCH v7] mm/page_alloc.c: memory_hotplug: free pages as higher order Message-ID: <20190109084031.GN31793@dhcp22.suse.cz> References: <1546578076-31716-1-git-send-email-arunks@codeaurora.org> <20190108181352.GI31793@dhcp22.suse.cz> <20190109073718.GM31793@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Arun KS Cc: Alexander Duyck , arunks.linux@gmail.com, akpm@linux-foundation.org, vbabka@suse.cz, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, getarunks@gmail.com On Wed 09-01-19 13:58:50, Arun KS wrote: > On 2019-01-09 13:07, Michal Hocko wrote: > > On Wed 09-01-19 11:28:52, Arun KS wrote: > > > On 2019-01-08 23:43, Michal Hocko wrote: > > > > On Tue 08-01-19 09:56:09, Alexander Duyck wrote: > > > > > On Fri, 2019-01-04 at 10:31 +0530, Arun KS wrote: > > > > [...] > > > > > > static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, > > > > > > void *arg) > > > > > > { > > > > > > - unsigned long i; > > > > > > unsigned long onlined_pages = *(unsigned long *)arg; > > > > > > - struct page *page; > > > > > > > > > > > > if (PageReserved(pfn_to_page(start_pfn))) > > > > > > - for (i = 0; i < nr_pages; i++) { > > > > > > - page = pfn_to_page(start_pfn + i); > > > > > > - (*online_page_callback)(page); > > > > > > - onlined_pages++; > > > > > > - } > > > > > > + onlined_pages = online_pages_blocks(start_pfn, nr_pages); > > > > > > > > > > Shouldn't this be a "+=" instead of an "="? It seems like you are > > > > > going > > > > > to lose your count otherwise. > > > > > > > > You are right of course. I should have noticed during the review. > > > > Thanks! > > > > > > I think we don't need to. The caller function is setting > > > onlined_pages = 0 > > > before calling online_pages_range(). > > > And there are no other reference to online_pages_range other than from > > > online_pages(). > > > > Are you missing that we accumulate onlined_pages via > > *(unsigned long *)arg = onlined_pages; > > in online_pages_range? > > In my testing I didn't find any problem. To match the code being replaced > and to avoid any corner cases, it is better to use += > Will update the patch. Have you checked that the number of present pages both in the zone and the node is correct because I fail to see how that would be possible. -- Michal Hocko SUSE Labs