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 E6255ECDE20 for ; Wed, 11 Sep 2019 12:19:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE6852084F for ; Wed, 11 Sep 2019 12:19:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568204386; bh=6WRpKouEe1TD+L5kJBxIYz+iT0recCfEkaX9dNyx0FE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=PP0riXQLq4Tj+jix1bE6Soj8yrrKG1F4bXbhxZo/wFfW/5vDZsQ9a+WEvv82KPCTl GScNPJNFJX7Sie4F0prUPFXfcuq8OJjaOe0mJnGXHSmNEiKiPznneGegSU321WIdKA UT45eCC0Lmb55bwu2X8UM+Boub9XngBDJsTr5JQI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727779AbfIKMTp (ORCPT ); Wed, 11 Sep 2019 08:19:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:58008 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726911AbfIKMTp (ORCPT ); Wed, 11 Sep 2019 08:19:45 -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 2C828B667; Wed, 11 Sep 2019 12:19:42 +0000 (UTC) Date: Wed, 11 Sep 2019 14:19:41 +0200 From: Michal Hocko To: "Michael S. Tsirkin" Cc: Alexander Duyck , Alexander Duyck , virtio-dev@lists.oasis-open.org, kvm list , 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" Subject: Re: [PATCH v9 0/8] stg mail -e --version=v9 \ Message-ID: <20190911121941.GU4023@dhcp22.suse.cz> References: <20190907172225.10910.34302.stgit@localhost.localdomain> <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> <20190911080804-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190911080804-mutt-send-email-mst@kernel.org> 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 Wed 11-09-19 08:08:38, Michael S. Tsirkin wrote: > On Wed, Sep 11, 2019 at 01:36:19PM +0200, 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. > > > > I remember that there was an attempt to report free memory that provided > > a callback mechanism [1], which was much less intrusive to the internals > > of the allocator yet it should provide a similar functionality. Did you > > see that approach? How does this compares to it? Or am I completely off > > when comparing them? > > > > [1] mostly likely not the latest version of the patchset > > http://lkml.kernel.org/r/1502940416-42944-5-git-send-email-wei.w.wang@intel.com > > Linus nacked that one. He thinks invoking callbacks with lots of > internal mm locks is too fragile. I would be really curious how much he would be happy about injecting other restrictions on the allocator like this patch proposes. This is more intrusive as it has a higher maintenance cost longterm IMHO. -- Michal Hocko SUSE Labs