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Tsirkin" 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-Disposition: inline In-Reply-To: <20190911080804-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190911_051945_110924_0BDD58AA X-CRM114-Status: GOOD ( 19.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yang Zhang , Pankaj Gupta , kvm list , David Hildenbrand , Catalin Marinas , Alexander Duyck , lcapitulino@redhat.com, linux-mm , Alexander Duyck , will@kernel.org, Andrea Arcangeli , virtio-dev@lists.oasis-open.org, Rik van Riel , Matthew Wilcox , "Wang, Wei W" , ying.huang@intel.com, Konrad Rzeszutek Wilk , Dan Williams , linux-arm-kernel@lists.infradead.org, Oscar Salvador , Nitesh Narayan Lal , Dave Hansen , LKML , Paolo Bonzini , Andrew Morton , Fengguang Wu , "Kirill A. Shutemov" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel