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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 0C744ECDE27 for ; Thu, 12 Sep 2019 07:16:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5F95214DE for ; Thu, 12 Sep 2019 07:16:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568272599; bh=jg0ekBBd7viHiLq8tPm9TGNc7PY5WFJZ1o2CJLiCTew=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mdIlR6cK9CCHkxMHhY9TbsM5vwfIbWG8+mRXYlEl2yDRzBVhmuj3Abjtyp1wmrXFz O24+CoZmgzI1POTCGy6Qv+g2gTmxYSN0LzjlOIytwqIV3QBP9tw2mdasIOCfrvzsRB zbxvqnNf9cUT1dESMbUrZUCaiFW9p4NmmW2yuIx8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729763AbfILHQh (ORCPT ); Thu, 12 Sep 2019 03:16:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:40482 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728927AbfILHQh (ORCPT ); Thu, 12 Sep 2019 03:16:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DA634AE35; Thu, 12 Sep 2019 07:16:34 +0000 (UTC) Date: Thu, 12 Sep 2019 09:16:33 +0200 From: Michal Hocko To: David Hildenbrand Cc: "Michael S. Tsirkin" , Alexander Duyck , Alexander Duyck , virtio-dev@lists.oasis-open.org, kvm list , Catalin Marinas , Dave Hansen , LKML , Matthew Wilcox , linux-mm , Andrew Morton , will@kernel.org, linux-arm-kernel@lists.infradead.org, Oscar Salvador , Yang Zhang , Pankaj Gupta , Konrad Rzeszutek Wilk , Nitesh Narayan Lal , Rik van Riel , lcapitulino@redhat.com, "Wang, Wei W" , Andrea Arcangeli , ying.huang@intel.com, Paolo Bonzini , Dan Williams , Fengguang Wu , "Kirill A. Shutemov" Subject: Re: [PATCH v9 0/8] stg mail -e --version=v9 \ Message-ID: <20190912071633.GL4023@dhcp22.suse.cz> References: <20190911113619.GP4023@dhcp22.suse.cz> <20190911080804-mutt-send-email-mst@kernel.org> <20190911121941.GU4023@dhcp22.suse.cz> <20190911122526.GV4023@dhcp22.suse.cz> <4748a572-57b3-31da-0dde-30138e550c3a@redhat.com> <20190911125413.GY4023@dhcp22.suse.cz> <736594d6-b9ae-ddb9-2b96-85648728ef33@redhat.com> <20190911132002.GA4023@dhcp22.suse.cz> <20190911135100.GC4023@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed 11-09-19 18:09:18, David Hildenbrand wrote: > On 11.09.19 15:51, Michal Hocko wrote: > > On Wed 11-09-19 15:20:02, Michal Hocko wrote: > > [...] > >>> 4. Continuously report, not the "one time report everything" approach. > >> > >> So you mean the allocator reporting this rather than an external code to > >> poll right? I do not know, how much this is nice to have than must have? > > > > Another idea that I haven't really thought through so it might turned > > out to be completely bogus but let's try anyway. Your "report everything" > > just made me look and realize that free_pages_prepare already performs > > stuff that actually does something similar yet unrelated. > > > > We do report to special page poisoning, zeroying or > > CONFIG_DEBUG_PAGEALLOC to unmap the address from the kernel address > > space. This sounds like something fitting your model no? > > > > AFAIKS, the poisoning/unmapping is done whenever a page is freed. I > don't quite see yet how that would help to remember if a page was > already reported. Do you still have to differ that state when each page is reported? > After reporting the page we would have to switch some > state (Nitesh: bitmap bit, Alexander: page flag) to identify that. Yes, you can either store the state somewhere. > Of course, we could map the page and treat that as "the state" when we > reported it, but I am not sure that's such a good idea :) > > As always, I might be very wrong ... I still do not fully understand the usecase so I might be equally wrong. My thinking is along these lines. Why should you scan free pages when you can effectively capture each freed page? If you go one step further then post_alloc_hook would be the counterpart to know that your page has been allocated. -- Michal Hocko SUSE Labs