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=-2.5 required=3.0 tests=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 24426C49ED6 for ; Wed, 11 Sep 2019 12:19:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DAD68206A1 for ; Wed, 11 Sep 2019 12:19:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DAD68206A1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 76AB06B000A; Wed, 11 Sep 2019 08:19:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 71BF66B000C; Wed, 11 Sep 2019 08:19:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 631C16B000D; Wed, 11 Sep 2019 08:19:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0056.hostedemail.com [216.40.44.56]) by kanga.kvack.org (Postfix) with ESMTP id 425D66B000A for ; Wed, 11 Sep 2019 08:19:45 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id D099C181AC9B4 for ; Wed, 11 Sep 2019 12:19:44 +0000 (UTC) X-FDA: 75922545888.27.mine00_37ec5446e1a5a X-HE-Tag: mine00_37ec5446e1a5a X-Filterd-Recvd-Size: 4375 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Wed, 11 Sep 2019 12:19:44 +0000 (UTC) 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) 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 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