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 0FB95C47403 for ; Thu, 12 Sep 2019 11:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DAF33214DA for ; Thu, 12 Sep 2019 11:11:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568286715; bh=Y2X0YoJuT6LuLpuDC0BxBW8mvEAqFEA1jWDaxQpXLKg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=t3YrcrDh7HFCbrTzHuleedqo4LmCV3Pn02LZQubAR6CVsuVnhEXYLwWE0FABed+Ij RCbRzZmrHMTgHnXn7I8bmOxgRGoGt/ye2wXvJO3GXOl8kuH+N02azZ6CV5W+HODUzX zjsj+enAMvp9lWNrVfS1TcFGBvvcJBi3A25ZFA4o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731313AbfILLLz (ORCPT ); Thu, 12 Sep 2019 07:11:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:55794 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730268AbfILLLy (ORCPT ); Thu, 12 Sep 2019 07:11:54 -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 1AB9AB764; Thu, 12 Sep 2019 11:11:52 +0000 (UTC) Date: Thu, 12 Sep 2019 13:11:50 +0200 From: Michal Hocko To: "Kirill A. Shutemov" Cc: Alexander Duyck , Alexander Duyck , virtio-dev@lists.oasis-open.org, kvm list , "Michael S. Tsirkin" , Catalin Marinas , David Hildenbrand , 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" , Mel Gorman , Vlastimil Babka Subject: Re: [PATCH v9 0/8] stg mail -e --version=v9 \ Message-ID: <20190912111150.GQ4023@dhcp22.suse.cz> References: <20190910124209.GY2063@dhcp22.suse.cz> <20190910144713.GF2063@dhcp22.suse.cz> <20190910175213.GD4023@dhcp22.suse.cz> <1d7de9f9f4074f67c567dbb4cc1497503d739e30.camel@linux.intel.com> <20190911113619.GP4023@dhcp22.suse.cz> <20190912091925.GM4023@dhcp22.suse.cz> <20190912102425.wzhhe6ygfgg64sma@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190912102425.wzhhe6ygfgg64sma@box> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 12-09-19 13:24:25, Kirill A. Shutemov wrote: > On Thu, Sep 12, 2019 at 11:19:25AM +0200, Michal Hocko wrote: > > On Wed 11-09-19 08:12:03, Alexander Duyck wrote: > > > On Wed, Sep 11, 2019 at 4:36 AM Michal Hocko wrote: > > > > > > > > On Tue 10-09-19 14:23:40, Alexander Duyck wrote: > > > > [...] > > > > > We don't put any limitations on the allocator other then that it needs to > > > > > clean up the metadata on allocation, and that it cannot allocate a page > > > > > that is in the process of being reported since we pulled it from the > > > > > free_list. If the page is a "Reported" page then it decrements the > > > > > reported_pages count for the free_area and makes sure the page doesn't > > > > > exist in the "Boundary" array pointer value, if it does it moves the > > > > > "Boundary" since it is pulling the page. > > > > > > > > This is still a non-trivial limitation on the page allocation from an > > > > external code IMHO. I cannot give any explicit reason why an ordering on > > > > the free list might matter (well except for page shuffling which uses it > > > > to make physical memory pattern allocation more random) but the > > > > architecture seems hacky and dubious to be honest. It shoulds like the > > > > whole interface has been developed around a very particular and single > > > > purpose optimization. > > > > > > How is this any different then the code that moves a page that will > > > likely be merged to the tail though? > > > > I guess you are referring to the page shuffling. If that is the case > > then this is an integral part of the allocator for a reason and it is > > very well obvious in the code including the consequences. I do not > > really like an idea of hiding similar constrains behind a generic > > looking feature which is completely detached from the allocator and so > > any future change of the allocator might subtly break it. > > I don't necessary follow why shuffling is more integral to page allocator > than reporting would be. It's next to shutffle.c under mm/ and integrated > in a simillar way. The main difference from my understanding is that the page reporting is a more generic looking feature which might grow different users over time yet there is a hardcoded set of restrictions to the allocator. Page shuffling is an integral part of the allocator without any other visibility outside. -- Michal Hocko SUSE Labs