From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50557) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vq5XH-0007lp-QL for qemu-devel@nongnu.org; Mon, 09 Dec 2013 13:26:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Vq5XB-0002Jj-QO for qemu-devel@nongnu.org; Mon, 09 Dec 2013 13:26:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:29492) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vq5XB-0002Je-I8 for qemu-devel@nongnu.org; Mon, 09 Dec 2013 13:26:21 -0500 Message-ID: <52A60B3D.6000604@redhat.com> Date: Mon, 09 Dec 2013 19:26:05 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1386143939-19142-1-git-send-email-gaowanlong@cn.fujitsu.com> <52A1939D.1080709@redhat.com> <20131206184936.GA10903@amt.cnet> <52A5FEF5.1010504@redhat.com> <20131209181032.GA8315@amt.cnet> In-Reply-To: <20131209181032.GA8315@amt.cnet> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V17 00/11] Add support for binding guest numa nodes to host numa nodes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcelo Tosatti Cc: drjones@redhat.com, ehabkost@redhat.com, lersek@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, bsd@redhat.com, anthony@codemonkey.ws, hutao@cn.fujitsu.com, y-goto@jp.fujitsu.com, peter.huangpeng@huawei.com, afaerber@suse.de, Wanlong Gao Il 09/12/2013 19:10, Marcelo Tosatti ha scritto: > On Mon, Dec 09, 2013 at 06:33:41PM +0100, Paolo Bonzini wrote: >> Il 06/12/2013 19:49, Marcelo Tosatti ha scritto: >>>>> You'll have with your patches (without them it's worse of course): >>>>> >>>>> RAM offset physical address node 0 >>>>> 0-3840M 0-3840M host node 0 >>>>> 4096M-4352M 4096M-4352M host node 0 >>>>> 4352M-8192M 4352M-8192M host node 1 >>>>> 3840M-4096M 8192M-8448M host node 1 >>>>> >>>>> So only 0-3G and 5-8G are aligned, 3G-5G and 8G-8.25G cannot use >>>>> gigabyte pages because they are split across host nodes. >>> AFAIK the TLB caches virt->phys translations, why specifics of >>> a given phys address is a factor into TLB caching? >> >> The problem is that "-numa mem" receives memory sizes and these do not >> take into account the hole below 4G. >> >> Thus, two adjacent host-physical addresses (two adjacent ram_addr_t-s) >> map to very far guest-physical addresses, are assigned to different >> guest nodes, and from there to different host nodes. In the above >> example this happens for 3G-5G. > > Physical address which is what the TLB uses does not take node > information into account. Indeed. What I should have written is "two adjacent host-virtual addresses". >> On second thought, this is not particularly important, or at least not >> yet. It's not really possible to control the NUMA policy for >> hugetlbfs-allocated memory, right? > > It is possible. I don't know what happens if conflicting NUMA policies > are specified for different virtual address ranges that map to a single > huge page. So what will happen is that 3G-5G will use GB pages but it will not be on the requested node. Paolo