Hi, Just wondering what the best route to take is. We have been running 32bit Dom0s for the past few years but we are refreshing all our hardware and the question is to which route we take. I assume we can run 32bit domUs ok on 64bit dom0? What is everyone else doing? Any issues? Thanks Ian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
iS-Fun Internet Services GmbH, Holger Diehm
2010-Jan-25 23:58 UTC
Re: [Xen-users] 32bit or 64bit dom0?
Hello, your question is just right for me to tell about my experiences of the last two weeks, when I migrated some older xen Dom0 installs to newer xen versions. I can only talk about pv, because thats the only thing we need (atm). First I set up two new 64bit Dom0 Debian servers. Compilation of xen 3.4.2 from source worked fine.ocumentation set aside - I don''t need it. I directly booted into an 2.6.31.12 xenified kernel - 64 bit - this kernel so far works like a charm - search the list for the patches for 2.6.31. The 2.6.18.8 Kernel from the xen-mercurial tree was built for some legacy DomU-32bit-Systems, which threw me libsysfs Errors on boot (some earlier SuSes) - works as expected too :-) These legacy Systems were on a xen 2.0.x and have to run on for some more time, the "newer" were migrated from xen 3.0.x. As you can see, just any paravirtualized DomU - 32 or 64 bit run on that 64bit xen-Dom0 just fine. I booted in various GNU/Linux system-flavours just swapping my xenified kernel with the distribution-kernel - centos,SuSe,debian,gentoo. The interesting point is, that a recent 32bit DomU even runs with the 64bit-Kernel - but very soon I decided to build an extra 32bit DomU-kernel, just to not confuse any tool that depends on the arch reported by the kernel - build tools etc can be easily confused by a wrong "uname". So I have three different kernels - 2.6.31.12Dom[0U]64bit, 2.6.31.12DomU 32 bit an 2.6.18.8DomU 32 bit - all 32bit Kernels are PAE-enabled. I ran several tests and there is just nothing ugly to report :-) 32 bit VMs run alongside 64 bit VMs, no Problems. The basics are reported everywhere - old xens allowed to have the tty1 as console . Rename all tty1 to xvc0... see inittab, securetty, and settings for console in the DomU configuration, if you haven''t already. Perhaps create the device under /dev - if not available. If you use filebased Images, switch from file: to tap:aio: in your DomU config file. It works well and you don''t run into any loop-device issues. What I often thought is a mistake, was my helping-hand with those old "unportable" DomUs...the "ancient" but still maintained 2.6.18.8 kernel from xen-mercurial. None of them ole DomUs ran with a recent kernel ! That is perhaps one thing you should *really* take into account for your Upgrade - test the DomUs with the newer Kernels you plan to use, and if you run into troubles, look for a matching xenified-kernel. This made it a nice job for me to migrate old xen DomUs to newer versions. So I couldn''t tell you the route to take, but perhaps some of the above "signs" help yout to take your route "your way". So thanks to all the guys who feel responsible to push xen forward..not only to newer kernels :-) And to all the unnamed contributors. Cheers, Holger Am Monday 25 January 2010 21:08:06 schrieb Ian Tobin:> Hi, > > > > Just wondering what the best route to take is. We have been running > 32bit Dom0s for the past few years but we are refreshing all our > hardware and the question is to which route we take. > > > > I assume we can run 32bit domUs ok on 64bit dom0? > > > > What is everyone else doing? Any issues? > > > > Thanks > > > > Ian_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 12:58:33AM +0100, iS-Fun Internet Services GmbH, Holger Diehm wrote:> Hello, > > your question is just right for me to tell about my experiences of the last > two weeks, when I migrated some older xen Dom0 installs to newer xen > versions. > I can only talk about pv, because thats the only thing we need (atm). > First I set up two new 64bit Dom0 Debian servers. Compilation of xen 3.4.2 > from source worked fine.ocumentation set aside - I don''t need it. > I directly booted into an 2.6.31.12 xenified kernel - 64 bit - this kernel so > far works like a charm - search the list for the patches for 2.6.31. > > The 2.6.18.8 Kernel from the xen-mercurial tree was built for some legacy > DomU-32bit-Systems, which threw me libsysfs Errors on boot (some earlier > SuSes) - works as expected too :-) > > These legacy Systems were on a xen 2.0.x and have to run on for some more > time, the "newer" were migrated from xen 3.0.x. > > As you can see, just any paravirtualized DomU - 32 or 64 bit run on that 64bit > xen-Dom0 just fine. > I booted in various GNU/Linux system-flavours just swapping my xenified kernel > with the distribution-kernel - centos,SuSe,debian,gentoo. > The interesting point is, that a recent 32bit DomU even runs with the > 64bit-Kernel - but very soon I decided to build an extra 32bit DomU-kernel, > just to not confuse any tool that depends on the arch reported by the > kernel - build tools etc can be easily confused by a wrong "uname". > > So I have three different kernels - 2.6.31.12Dom[0U]64bit, 2.6.31.12DomU 32 > bit an 2.6.18.8DomU 32 bit - all 32bit Kernels are PAE-enabled. > I ran several tests and there is just nothing ugly to report :-) > 32 bit VMs run alongside 64 bit VMs, no Problems. > > The basics are reported everywhere - old xens allowed to have the tty1 as > console . Rename all tty1 to xvc0... see inittab, securetty, and settings for > console in the DomU configuration, if you haven''t already. > Perhaps create the device under /dev - if not available. > If you use filebased Images, switch from file: to tap:aio: in your DomU config > file. It works well and you don''t run into any loop-device issues. > > What I often thought is a mistake, was my helping-hand with those > old "unportable" DomUs...the "ancient" but still maintained 2.6.18.8 kernel > from xen-mercurial. > None of them ole DomUs ran with a recent kernel ! > That is perhaps one thing you should *really* take into account for your > Upgrade - test the DomUs with the newer Kernels you plan to use, and if you > run into troubles, look for a matching xenified-kernel. > This made it a nice job for me to migrate old xen DomUs to newer versions. > > So I couldn''t tell you the route to take, but perhaps some of the > above "signs" help yout to take your route "your way". > > So thanks to all the guys who feel responsible to push xen forward..not only > to newer kernels :-) And to all the unnamed contributors. >Good to hear it worked OK :) I think there''s still one Xen 2.0.x server running that I''ve installed.. it has been very stable:) -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Thanks for the info guys, ive been playing with 3.4.2 on 32bits but im thinking for the future it would be worth having 64bits for things like win2008R2 as this is 64 bit only. Ill build a new server and do some tests :) Many thanks Ian -----Original Message----- From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Pasi Kärkkäinen Sent: 26 January 2010 07:28 To: iS-Fun Internet Services GmbH, Holger Diehm Cc: xen-users@lists.xensource.com Subject: Re: [Xen-users] 32bit or 64bit dom0? On Tue, Jan 26, 2010 at 12:58:33AM +0100, iS-Fun Internet Services GmbH, Holger Diehm wrote:> Hello, > > your question is just right for me to tell about my experiences of the last > two weeks, when I migrated some older xen Dom0 installs to newer xen > versions. > I can only talk about pv, because thats the only thing we need (atm). > First I set up two new 64bit Dom0 Debian servers. Compilation of xen 3.4.2 > from source worked fine.ocumentation set aside - I don''t need it. > I directly booted into an 2.6.31.12 xenified kernel - 64 bit - this kernel so > far works like a charm - search the list for the patches for 2.6.31. > > The 2.6.18.8 Kernel from the xen-mercurial tree was built for some legacy > DomU-32bit-Systems, which threw me libsysfs Errors on boot (some earlier > SuSes) - works as expected too :-) > > These legacy Systems were on a xen 2.0.x and have to run on for some more > time, the "newer" were migrated from xen 3.0.x. > > As you can see, just any paravirtualized DomU - 32 or 64 bit run on that 64bit > xen-Dom0 just fine. > I booted in various GNU/Linux system-flavours just swapping my xenified kernel > with the distribution-kernel - centos,SuSe,debian,gentoo. > The interesting point is, that a recent 32bit DomU even runs with the > 64bit-Kernel - but very soon I decided to build an extra 32bit DomU-kernel, > just to not confuse any tool that depends on the arch reported by the > kernel - build tools etc can be easily confused by a wrong "uname". > > So I have three different kernels - 2.6.31.12Dom[0U]64bit, 2.6.31.12DomU 32 > bit an 2.6.18.8DomU 32 bit - all 32bit Kernels are PAE-enabled. > I ran several tests and there is just nothing ugly to report :-) > 32 bit VMs run alongside 64 bit VMs, no Problems. > > The basics are reported everywhere - old xens allowed to have the tty1 as > console . Rename all tty1 to xvc0... see inittab, securetty, and settings for > console in the DomU configuration, if you haven''t already. > Perhaps create the device under /dev - if not available. > If you use filebased Images, switch from file: to tap:aio: in your DomU config > file. It works well and you don''t run into any loop-device issues. > > What I often thought is a mistake, was my helping-hand with those > old "unportable" DomUs...the "ancient" but still maintained 2.6.18.8 kernel > from xen-mercurial. > None of them ole DomUs ran with a recent kernel ! > That is perhaps one thing you should *really* take into account for your > Upgrade - test the DomUs with the newer Kernels you plan to use, and if you > run into troubles, look for a matching xenified-kernel. > This made it a nice job for me to migrate old xen DomUs to newer versions. > > So I couldn''t tell you the route to take, but perhaps some of the > above "signs" help yout to take your route "your way". > > So thanks to all the guys who feel responsible to push xen forward..not only > to newer kernels :-) And to all the unnamed contributors. >Good to hear it worked OK :) I think there''s still one Xen 2.0.x server running that I''ve installed.. it has been very stable:) -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <itobin@tidyhosts.com> wrote:> Thanks for the info guys, ive been playing with 3.4.2 on 32bits but im thinking for the future it would be worth having 64bits for things like win2008R2 as this is 64 bit only.If Windows is your only concern, IIRC 32bit xen can run 64bit HVM domUs just fine. What does "xm info" say about caps? Personally I use 64bit xen, dom0, and domU so it would be easier when I need to assign one of them with memory over 4GB, since using 32bit PAE has some performance penalty. -- Fajar _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha wrote:> On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <itobin@tidyhosts.com> wrote: > > Thanks for the info guys, ive been playing with 3.4.2 on 32bits but im thinking for the future it would be worth having 64bits for things like win2008R2 as this is 64 bit only. > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > domUs just fine. What does "xm info" say about caps? >I think you need 64b Xen hypervisor to run 64b guests, but dom0 Linux can be still 32bit PAE.> Personally I use 64bit xen, dom0, and domU so it would be easier when > I need to assign one of them with memory over 4GB, since using 32bit > PAE has some performance penalty. >I think there was some benchmarks about this recently and the PAE performance hit wasn''t very big.. Anyway, it''s better to use 64b nowadays. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 7:31 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha wrote: > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <itobin@tidyhosts.com> wrote: > > > Thanks for the info guys, ive been playing with 3.4.2 on 32bits but im > thinking for the future it would be worth having 64bits for things like > win2008R2 as this is 64 bit only. > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > domUs just fine. What does "xm info" say about caps? > > > > I think you need 64b Xen hypervisor to run 64b guests, > but dom0 Linux can be still 32bit PAE. > > > Personally I use 64bit xen, dom0, and domU so it would be easier when > > I need to assign one of them with memory over 4GB, since using 32bit > > PAE has some performance penalty. > > > > I think there was some benchmarks about this recently and the > PAE performance hit wasn''t very big.. > > Anyway, it''s better to use 64b nowadays. > > -- Pasi > >That depends one whether you consider (up to) 20% worth considering! I''d be willing to change for 5%. http://www.phoronix.com/scan.php?page=article&item=616&num=1 Grant McWilliams _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote:> On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen <[1]pasik@iki.fi> > wrote: > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha wrote: > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <[2]itobin@tidyhosts.com> > wrote: > > > Thanks for the info guys, ive been playing with 3.4.2 on 32bits but > im thinking for the future it would be worth having 64bits for things > like win2008R2 as this is 64 bit only. > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > domUs just fine. What does "xm info" say about caps? > > > > I think you need 64b Xen hypervisor to run 64b guests, > but dom0 Linux can be still 32bit PAE. > > Personally I use 64bit xen, dom0, and domU so it would be easier when > > I need to assign one of them with memory over 4GB, since using 32bit > > PAE has some performance penalty. > > > > I think there was some benchmarks about this recently and the > PAE performance hit wasn''t very big.. > > Anyway, it''s better to use 64b nowadays. > -- Pasi > > That depends one whether you consider (up to) 20% worth considering! I''d > be willing to change for 5%. > > [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 >Hmm.. did you paste wrong url? That url only has 32b vs. 64b? Here''s 32b vs. 32b PAE benchmark: http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae Although that benchmark must have something wrong with the 32 vs 64 numbers.. the different can''t be THAT big. "In the fourteen tests for this article we did not find using Ubuntu''s 32-bit PAE kernel to have a dramatic performance impact whether it be positive or negative. Granted, we were using just 4GB of system memory that is common to many desktops, but if using 8GB, 16GB, or even a greater memory capacity the performance penalties are perhaps higher. " -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 8:45 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote: > > On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen <[1]pasik@iki.fi> > > wrote: > > > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha wrote: > > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <[2] > itobin@tidyhosts.com> > > wrote: > > > > Thanks for the info guys, ive been playing with 3.4.2 on 32bits > but > > im thinking for the future it would be worth having 64bits for > things > > like win2008R2 as this is 64 bit only. > > > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > > domUs just fine. What does "xm info" say about caps? > > > > > > > I think you need 64b Xen hypervisor to run 64b guests, > > but dom0 Linux can be still 32bit PAE. > > > Personally I use 64bit xen, dom0, and domU so it would be easier > when > > > I need to assign one of them with memory over 4GB, since using > 32bit > > > PAE has some performance penalty. > > > > > > > I think there was some benchmarks about this recently and the > > PAE performance hit wasn''t very big.. > > > > Anyway, it''s better to use 64b nowadays. > > -- Pasi > > > > That depends one whether you consider (up to) 20% worth considering! > I''d > > be willing to change for 5%. > > > > [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 > > > > Hmm.. did you paste wrong url? That url only has 32b vs. 64b? > > Here''s 32b vs. 32b PAE benchmark: > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > > Although that benchmark must have something wrong with the 32 vs 64 > numbers.. > the different can''t be THAT big. > > "In the fourteen tests for this article we did not find using Ubuntu''s > 32-bit PAE kernel > to have a dramatic performance impact whether it be positive or negative. > > Granted, we were using just 4GB of system memory that is common to many > desktops, > but if using 8GB, 16GB, or even a greater memory capacity the performance > penalties are perhaps higher. " > > -- Pasi > >Yes I did! Thanks. Here try this. http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 Grant McWilliams _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > -- Pasi >> > >> > That depends one whether you consider (up to) 20% worth considering! >> I''d >> > be willing to change for 5%. >> > >> > [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 >> > >> >> Hmm.. did you paste wrong url? That url only has 32b vs. 64b? >> >> Here''s 32b vs. 32b PAE benchmark: >> http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae >> >> Although that benchmark must have something wrong with the 32 vs 64 >> numbers.. >> the different can''t be THAT big. >> >> "In the fourteen tests for this article we did not find using Ubuntu''s >> 32-bit PAE kernel >> to have a dramatic performance impact whether it be positive or negative. >> >> Granted, we were using just 4GB of system memory that is common to many >> desktops, >> but if using 8GB, 16GB, or even a greater memory capacity the performance >> penalties are perhaps higher. " >> >> -- Pasi >> >> > > Yes I did! Thanks. Here try this. > > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > > Grant McWilliams >I either posted two quick or too late! So the quote was saying that PAE didn''t have an impact over a stock 32 bit kernel but if you compare it to the 64 bit kernel there''s a serious hit. In the tests they did the 64 bit kernel was faster by quite a bit in every way. I''ve blindly been using 64 bit kernels wherever possible but this helps me know that I''ve benefited from it. Grant McWilliams _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Many people also forget about the performance boost on CPU intensive apps by running 64 bit mode, even if you don''t need extra memory. This can be a 5%-15% depending on the application. This includes the OS. The reason is 64 bit mode not only allows 64 bit memory access and registers, but it also doubles the number of registers available. I would always recommend to use 64 bit whenever possible unless there is a pressing need to stick with 32 bit. S.W. On 1/26/2010 11:05 AM, Grant McWilliams wrote:> > On Tue, Jan 26, 2010 at 8:45 AM, Pasi Kärkkäinen <pasik@iki.fi > <mailto:pasik@iki.fi>> wrote: > > On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote: > > On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen > <[1]pasik@iki.fi <mailto:pasik@iki.fi>> > > wrote: > > > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha > wrote: > > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin > <[2]itobin@tidyhosts.com <mailto:itobin@tidyhosts.com>> > > wrote: > > > > Thanks for the info guys, ive been playing with 3.4.2 on > 32bits but > > im thinking for the future it would be worth having 64bits > for things > > like win2008R2 as this is 64 bit only. > > > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > > domUs just fine. What does "xm info" say about caps? > > > > > > > I think you need 64b Xen hypervisor to run 64b guests, > > but dom0 Linux can be still 32bit PAE. > > > Personally I use 64bit xen, dom0, and domU so it would be > easier when > > > I need to assign one of them with memory over 4GB, since using > 32bit > > > PAE has some performance penalty. > > > > > > > I think there was some benchmarks about this recently and the > > PAE performance hit wasn''t very big.. > > > > Anyway, it''s better to use 64b nowadays. > > -- Pasi > > > > That depends one whether you consider (up to) 20% worth > considering! I''d > > be willing to change for 5%. > > > > > [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 > <http://www.phoronix.com/scan.php?page=article&item=616&num=1> > > > > Hmm.. did you paste wrong url? That url only has 32b vs. 64b? > > Here''s 32b vs. 32b PAE benchmark: > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > <http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae> > > Although that benchmark must have something wrong with the 32 vs > 64 numbers.. > the different can''t be THAT big. > > "In the fourteen tests for this article we did not find using > Ubuntu''s 32-bit PAE kernel > to have a dramatic performance impact whether it be positive or > negative. > > Granted, we were using just 4GB of system memory that is common to > many desktops, > but if using 8GB, 16GB, or even a greater memory capacity the > performance > penalties are perhaps higher. " > > -- Pasi > > > > Yes I did! Thanks. Here try this. > > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > <http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1> > > Grant McWilliams > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 09:09:00AM -0800, Grant McWilliams wrote:> > Â Â Â -- Pasi > > > > Â Â That depends one whether you consider (up to) 20% worth > considering! I''d > > Â Â be willing to change for 5%. > > > > Â > Â [3][1]http://www.phoronix.com/scan.php?page=article&item=616&num=1 > > > > Hmm.. did you paste wrong url? That url only has 32b vs. 64b? > > Here''s 32b vs. 32b PAE benchmark: > [2]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > > Although that benchmark must have something wrong with the 32 vs 64 > numbers.. > the different can''t be THAT big. > > "In the fourteen tests for this article we did not find using Ubuntu''s > 32-bit PAE kernel > to have a dramatic performance impact whether it be positive or > negative. > > Granted, we were using just 4GB of system memory that is common to > many desktops, > but if using 8GB, 16GB, or even a greater memory capacity the > performance > penalties are perhaps higher. " > -- Pasi > > Yes I did! Thanks. Here try this. > > [3]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > Grant McWilliams > > I either posted two quick or too late! So the quote was saying that PAE > didn''t have an impact over a stock 32 bit kernel > but if you compare it to the 64 bit kernel there''s a serious hit. In the > tests they did the 64 bit kernel was faster by quite a bit > in every way. I''ve blindly been using 64 bit kernels wherever possible but > this helps me know that I''ve benefited from it. >That "Apache Benchmark" must be wrong, THAT huge difference can''t be true. But yeah, in general 64b should be faster nowadays compared to 32b or 32b PAE, since it has a lot more registers to use etc.. 32b vs 32b PAE doesn''t seem to be big difference, at least not with 4 GB of RAM. Also PAE gives you possibility to use NX protection.. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Many people also forget about the performance boost on CPU intensive apps by running 64 bit mode, even if you don''t need extra memory. This can be a 5%-15% depending on the application. This includes the OS. The reason is 64 bit mode not only allows 64 bit memory access and registers, but it also doubles the number of registers available. I would always recommend to use 64 bit whenever possible unless there is a pressing need to stick with 32 bit. S.W. On 1/26/2010 11:05 AM, Grant McWilliams wrote:> > On Tue, Jan 26, 2010 at 8:45 AM, Pasi Kärkkäinen <pasik@iki.fi > <mailto:pasik@iki.fi>> wrote: > > On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote: > > On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen > <[1]pasik@iki.fi <mailto:pasik@iki.fi>> > > wrote: > > > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha > wrote: > > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin > <[2]itobin@tidyhosts.com <mailto:itobin@tidyhosts.com>> > > wrote: > > > > Thanks for the info guys, ive been playing with 3.4.2 on > 32bits but > > im thinking for the future it would be worth having 64bits > for things > > like win2008R2 as this is 64 bit only. > > > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > > domUs just fine. What does "xm info" say about caps? > > > > > > > I think you need 64b Xen hypervisor to run 64b guests, > > but dom0 Linux can be still 32bit PAE. > > > Personally I use 64bit xen, dom0, and domU so it would be > easier when > > > I need to assign one of them with memory over 4GB, since using > 32bit > > > PAE has some performance penalty. > > > > > > > I think there was some benchmarks about this recently and the > > PAE performance hit wasn''t very big.. > > > > Anyway, it''s better to use 64b nowadays. > > -- Pasi > > > > That depends one whether you consider (up to) 20% worth > considering! I''d > > be willing to change for 5%. > > > > > [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 > <http://www.phoronix.com/scan.php?page=article&item=616&num=1> > > > > Hmm.. did you paste wrong url? That url only has 32b vs. 64b? > > Here''s 32b vs. 32b PAE benchmark: > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > <http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae> > > Although that benchmark must have something wrong with the 32 vs > 64 numbers.. > the different can''t be THAT big. > > "In the fourteen tests for this article we did not find using > Ubuntu''s 32-bit PAE kernel > to have a dramatic performance impact whether it be positive or > negative. > > Granted, we were using just 4GB of system memory that is common to > many desktops, > but if using 8GB, 16GB, or even a greater memory capacity the > performance > penalties are perhaps higher. " > > -- Pasi > > > > Yes I did! Thanks. Here try this. > > http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > <http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1> > > Grant McWilliams > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Im sold on the 64bits J From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Steven Wilcoxon Sent: 26 January 2010 20:02 To: xen-users@lists.xensource.com Subject: Re: [Xen-users] 32bit or 64bit dom0? Many people also forget about the performance boost on CPU intensive apps by running 64 bit mode, even if you don't need extra memory. This can be a 5%-15% depending on the application. This includes the OS. The reason is 64 bit mode not only allows 64 bit memory access and registers, but it also doubles the number of registers available. I would always recommend to use 64 bit whenever possible unless there is a pressing need to stick with 32 bit. S.W. On 1/26/2010 11:05 AM, Grant McWilliams wrote: On Tue, Jan 26, 2010 at 8:45 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote: On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote:> On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen <[1]pasik@iki.fi>> wrote: > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha wrote:> > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin <[2]itobin@tidyhosts.com>> wrote: > > > Thanks for the info guys, ive been playing with 3.4.2 on 32bits but > im thinking for the future it would be worth having 64bits for things > like win2008R2 as this is 64 bit only. > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit HVM > > domUs just fine. What does "xm info" say about caps? > > > > I think you need 64b Xen hypervisor to run 64b guests, > but dom0 Linux can be still 32bit PAE. > > Personally I use 64bit xen, dom0, and domU so it would be easier when > > I need to assign one of them with memory over 4GB, since using 32bit > > PAE has some performance penalty. > > > > I think there was some benchmarks about this recently and the > PAE performance hit wasn't very big.. > > Anyway, it's better to use 64b nowadays. > -- Pasi > > That depends one whether you consider (up to) 20% worth considering! I'd > be willing to change for 5%. >> [3]http://www.phoronix.com/scan.php?page=article&item=616&num=1 >Hmm.. did you paste wrong url? That url only has 32b vs. 64b? Here's 32b vs. 32b PAE benchmark: http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae Although that benchmark must have something wrong with the 32 vs 64 numbers.. the different can't be THAT big. "In the fourteen tests for this article we did not find using Ubuntu's 32-bit PAE kernel to have a dramatic performance impact whether it be positive or negative. Granted, we were using just 4GB of system memory that is common to many desktops, but if using 8GB, 16GB, or even a greater memory capacity the performance penalties are perhaps higher. " -- Pasi Yes I did! Thanks. Here try this. http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 Grant McWilliams _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Jan 26, 2010 at 02:01:53PM -0600, Steven Wilcoxon wrote:> Many people also forget about the performance boost on CPU intensive apps > by running 64 bit mode, even if you don''t need extra memory. This can be a > 5%-15% depending on the application. This includes the OS. The reason is > 64 bit mode not only allows 64 bit memory access and registers, but it > also doubles the number of registers available. > > I would always recommend to use 64 bit whenever possible unless there is a > pressing need to stick with 32 bit. >64b apps use more memory than the same app on 32b.. and executables are bigger. But yeah, ram and disk are so cheap nowadays that 64b is the way to go. -- Pasi> S.W. > > On 1/26/2010 11:05 AM, Grant McWilliams wrote: > > On Tue, Jan 26, 2010 at 8:45 AM, Pasi Kärkkäinen <[1]pasik@iki.fi> > wrote: > > On Tue, Jan 26, 2010 at 08:30:40AM -0800, Grant McWilliams wrote: > > On Tue, Jan 26, 2010 at 7:31 AM, Pasi KÀrkkÀinen > <[1][2]pasik@iki.fi> > > wrote: > > > > On Tue, Jan 26, 2010 at 06:22:38PM +0700, Fajar A. Nugraha > wrote: > > > On Tue, Jan 26, 2010 at 3:06 PM, Ian Tobin > <[2][3]itobin@tidyhosts.com> > > wrote: > > > > Thanks for the info guys, ive been playing with 3.4.2 on > 32bits but > > im thinking for the future it would be worth having 64bits for > things > > like win2008R2 as this is 64 bit only. > > > > > > If Windows is your only concern, IIRC 32bit xen can run 64bit > HVM > > > domUs just fine. What does "xm info" say about caps? > > > > > > > I think you need 64b Xen hypervisor to run 64b guests, > > but dom0 Linux can be still 32bit PAE. > > > Personally I use 64bit xen, dom0, and domU so it would be > easier when > > > I need to assign one of them with memory over 4GB, since > using 32bit > > > PAE has some performance penalty. > > > > > > > I think there was some benchmarks about this recently and the > > PAE performance hit wasn''t very big.. > > > > Anyway, it''s better to use 64b nowadays. > > -- Pasi > > > > That depends one whether you consider (up to) 20% worth > considering! I''d > > be willing to change for 5%. > > > > > [3][4]http://www.phoronix.com/scan.php?page=article&item=616&num=1 > > > > Hmm.. did you paste wrong url? That url only has 32b vs. 64b? > > Here''s 32b vs. 32b PAE benchmark: > [5]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > > Although that benchmark must have something wrong with the 32 vs 64 > numbers.. > the different can''t be THAT big. > > "In the fourteen tests for this article we did not find using Ubuntu''s > 32-bit PAE kernel > to have a dramatic performance impact whether it be positive or > negative. > > Granted, we were using just 4GB of system memory that is common to > many desktops, > but if using 8GB, 16GB, or even a greater memory capacity the > performance > penalties are perhaps higher. " > -- Pasi > > Yes I did! Thanks. Here try this. > > [6]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > > Grant McWilliams > > _______________________________________________ > Xen-users mailing list > [7]Xen-users@lists.xensource.com > [8]http://lists.xensource.com/xen-users > > References > > Visible links > 1. mailto:pasik@iki.fi > 2. mailto:pasik@iki.fi > 3. mailto:itobin@tidyhosts.com > 4. http://www.phoronix.com/scan.php?page=article&item=616&num=1 > 5. http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae > 6. http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1 > 7. mailto:Xen-users@lists.xensource.com > 8. http://lists.xensource.com/xen-users> _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users