From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Shuklin Subject: Re: a ton of kernel issues Date: Wed, 14 Dec 2011 22:40:08 +0400 Message-ID: <4EE8ED88.8060107@gmail.com> References: <4EE675A8.3030609@niemail.de> <4EE71663.5040308@gmail.com> <4EE72A94.6040904@gmail.com> <4EE75080.1000909@citrix.com> <4EE7BE1B.6070509@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Fajar A. Nugraha" Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 14.12.2011 11:47, Fajar A. Nugraha wrote: >> Well... For us it make HUGE difference. We running cloud with very precise >> accounting of fast automaric memory allocation for customer's domains and >> we account them for ... em... KiB*hr value, so if we account domains based >> on xc.get_domain_memkb value and customers saw difference between TotalMem >> and our values this will make them feel like we cheating. We not greedy and >> ready to 'cut' our mem_kb value to their TotalMem, but I hasn't found any >> formula for that (calculate TotalMem from static-max and dom_kb values) and >> I can't trust any data from customer's domains (except request for memory we >> accept, serve and happily take money for 'more memory'). >> >> It sounds ridiculous, but we avoiding pv_ops kernels usage due that little >> ~50Mb steal. We stuck with -xen kernels (forward porting from SUSE and >> native CentOS 2.6.18-xen). I don't know what we will do in the future, but >> right now PV-ops is not good... > Why not just explain what really happened in a noob-friendly language? > > For example, when buying a computer with built-in graphic card, > MemTotal is always lower than the ammount of memory actually > installed. Yet a simple explanation "some of the memory is used by the > built-in graphic card" is enough, without having to go into details of > what is the formula to calculate how much memory actualy used. > Well, this is fine if we provide customers normal 'VDS-like' virtual machines. You getting 256MiB, some of it is used by kernel and not displayed as TotalMem. But we provide vm with ellastic memory (like 256MiB - 8GiB) with promise 'we will serve you enough memory to your applications and you will pay only for allocated memory for your VM'. User expects we give him + 2GiB for 2 min and we charge him for 2*2/60=0.066 GiB*hr. With -xen kernels they got exactly they paid (at least, with TotalMem value). If we saying them 'here something you don't understand' this will cause some doubts.