From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasiliy G Tolstov Subject: Re: failed to start centos 5 domU with maxmem=30000 Date: Fri, 13 Aug 2010 09:54:57 +0400 Message-ID: <1281678897.9689.5.camel@vase.work> References: <1281608645.5454.10.camel@vase.work> <20100812113731.GP2804@reaktio.net 1281613063.5454.15.camel@vase.work> <042d87c1-bb13-436b-a5ba-9ec1578d53d0@default> <1281615845.5454.20.camel@vase.work> <4C643EA2.1020300@goop.org> Reply-To: v.tolstov@selfip.ru Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <4C643EA2.1020300@goop.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jeremy Fitzhardinge Cc: Dan Magenheimer , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org =D0=92 =D0=A7=D1=82=D0=B2, 12/08/2010 =D0=B2 11:34 -0700, Jeremy Fitzhard= inge =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > On 08/12/2010 05:24 AM, Vasiliy G Tolstov wrote: > > =D0=92 =D0=A7=D1=82=D0=B2, 12/08/2010 =D0=B2 05:17 -0700, Dan Magenhe= imer =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >>> From: Vasiliy G Tolstov [mailto:v.tolstov@selfip.ru] > >>> Sent: Thursday, August 12, 2010 5:38 AM > >>> To: Pasi K=C3=A4rkk=C3=A4inen > >>> Cc: xen-devel@lists.xensource.com > >>> Subject: Re: [Xen-devel] failed to start centos 5 domU with > >>> maxmem=3D30000 > >>> > >>> =D0=92 =D0=A7=D1=82=D0=B2, 12/08/2010 =D0=B2 14:37 +0300, Pasi K=C3= =A4rkk=C3=A4inen =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >>>> On Thu, Aug 12, 2010 at 02:24:05PM +0400, Vasiliy G Tolstov wrote: > >>>>> Hello. I'm try to start centos domU pvm under sles 11 sp1 xen > >>> kernel > >>>>> with memory=3D512 and maxmem=3D30000. Centos doing boot and freez= e. > >>>>> If i'm try to use maxmem=3D15000 all works. > >>>>> > >>>>> Can You tell me what's wrong? > >>>>> > >>>> Is the centos PV domU 32bit or 64bit ? > >>> 64 bit kernel-xen. > >>> > >>> I found this in xen sources: > >>> > >>> /* Simple continuous piecewiese linear function: > >>> * max MiB -> min MiB gradient > >>> * 0 0 > >>> * 16 16 > >>> * 32 24 > >>> * 128 72 (1/2) > >>> * 512 168 (1/4) > >>> * 2048 360 (1/8) > >>> * 8192 552 (1/32) > >>> * 32768 1320 > >>> * 131072 4392 > >>> */ > >>> > >>> Why this is not provided in documentation or on web site? > >> Hi Vasily -- > >> > >> This function limits how far memory can be reduced when > >> ballooning a guest (including dom0). It is only a heuristic > >> but is intended to take into account the various overheads > >> a guest Linux kernel requires to manage memory to avoid > >> out-of-memory conditions. > >> > >> But I think you are correct... the same (or similar) > >> function should be published as it also serves as a > >> guideline for the ratio between memory=3D and maxmem=3D > >> parameters when creating a guest: If the ratio > >> of maxmem divided by memory is too high, the guest > >> will not even boot. > >> > > Is that possible to use memory=3D32 and maxmem=3D60000 ? >=20 > A factor of ~2000 between smallest and largest size won't work. The=20 > problem is that lots of kernel structures are scaled with the amount of= =20 > boot-time memory, and they'll simply be overloaded when you add more=20 > memory. For example, the page structure array for 60GB needs ~15.3=20 > million entries, which at 64 bytes per entry will take ~980MB... >=20 Ok. Thank You. Bu can some one provide correct ratio for memory and maxmemory that others not to make mistakes and not try to post bugs on that? =3D) > >> I am curious as to why you would specify memory=3D so > >> much smaller than maxmem=3D. Are you trying to overcommit > >> memory for guests that are often idle but sometimes use > >> a very large amount of memory? > > We want to provide ability to use small as possible memory if the gue= st > > is idle. And much as possible when the guest under heavy load. >=20 > This is exactly the use-case for the hotplug memory stuff Daniel is=20 > working on - which I guess is why you've been testing it. This is problem, because a'm using centos, debian, ubuntu, opensuse and other systems in domU, but i read that tmem support needed in dom0 and domU. Debian and Ubuntu i think, does not support this... But i'm try. --=20 Vasiliy G Tolstov Selfip.Ru