Hi guys, I need your help understanding this behavior: My host has 8GB RAM installed. Xen reports about 1.8G free memory with three domains running. xl info|grep memory total_memory : 7887 free_memory : 1833 xl list Name ID Mem VCPUs State Time(s) Domain-0 0 768 8 r----- 650.2 nas 1 3072 2 -b---- 704.0 windom 3 2047 4 r----- 520.7 Now, when I tried to launch a forth domain with 1G memory assigned, here is the result: xl list Name ID Mem VCPUs State Time(s) Domain-0 0 380 8 r----- 654.1 nas 1 3072 2 -b---- 706.7 windom 3 2047 4 r----- 529.8 freebsd 5 1024 1 -b---- 0.7 xl info|grep memory total_memory : 7887 free_memory : 1184 As you can see, hypervisor is ballooning memory from dom0 instead of allocating from free_memory. If I increase the guest memory of the new domain to 1.5G or 2G. It simply fails to launch, saying something like dom0 memory is below minimal threshold. This gives me the impression that the free_memory is fake. Is it an expected behavior? What are the remaining 1GB memory for? PS: I''m on the xen 4.3.0 release. Thanks, Timothy
Pasi Kärkkäinen
2013-Aug-12 06:15 UTC
Re: Free memory reported but not used in new domain creation?
On Mon, Aug 12, 2013 at 01:46:30PM +0800, G.R. wrote:> Hi guys, > I need your help understanding this behavior: > > My host has 8GB RAM installed. Xen reports about 1.8G free memory with > three domains running. > > xl info|grep memory > total_memory : 7887 > free_memory : 1833 > > xl list > Name ID Mem VCPUs State Time(s) > Domain-0 0 768 8 r----- 650.2 > nas 1 3072 2 -b---- 704.0 > windom 3 2047 4 r----- 520.7 > > Now, when I tried to launch a forth domain with 1G memory assigned, > here is the result: > > xl list > Name ID Mem VCPUs State Time(s) > Domain-0 0 380 8 r----- 654.1 > nas 1 3072 2 -b---- 706.7 > windom 3 2047 4 r----- 529.8 > freebsd 5 1024 1 -b---- 0.7 > > xl info|grep memory > total_memory : 7887 > free_memory : 1184 > > As you can see, hypervisor is ballooning memory from dom0 instead of > allocating from free_memory. If I increase the guest memory of the new > domain to 1.5G or 2G. It simply fails to launch, saying something like > dom0 memory is below minimal threshold. > > This gives me the impression that the free_memory is fake. Is it an > expected behavior? > What are the remaining 1GB memory for? > > PS: I''m on the xen 4.3.0 release. >Hello, This is a long-standing bug in xl. The workaround is to disable xl autoballooning.. http://wiki.xen.org/wiki/Xen_Best_Practices -- Pasi
On Mon, Aug 12, 2013 at 2:15 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:> On Mon, Aug 12, 2013 at 01:46:30PM +0800, G.R. wrote: >> Hi guys, >> I need your help understanding this behavior: >> >> My host has 8GB RAM installed. Xen reports about 1.8G free memory with >> three domains running. >> >> xl info|grep memory >> total_memory : 7887 >> free_memory : 1833 >> >> xl list >> Name ID Mem VCPUs State Time(s) >> Domain-0 0 768 8 r----- 650.2 >> nas 1 3072 2 -b---- 704.0 >> windom 3 2047 4 r----- 520.7 >> >> Now, when I tried to launch a forth domain with 1G memory assigned, >> here is the result: >> >> xl list >> Name ID Mem VCPUs State Time(s) >> Domain-0 0 380 8 r----- 654.1 >> nas 1 3072 2 -b---- 706.7 >> windom 3 2047 4 r----- 529.8 >> freebsd 5 1024 1 -b---- 0.7 >> >> xl info|grep memory >> total_memory : 7887 >> free_memory : 1184 >> >> As you can see, hypervisor is ballooning memory from dom0 instead of >> allocating from free_memory. If I increase the guest memory of the new >> domain to 1.5G or 2G. It simply fails to launch, saying something like >> dom0 memory is below minimal threshold. >> >> This gives me the impression that the free_memory is fake. Is it an >> expected behavior? >> What are the remaining 1GB memory for? >> >> PS: I''m on the xen 4.3.0 release. >> > > Hello, > > This is a long-standing bug in xl. > The workaround is to disable xl autoballooning.. > > http://wiki.xen.org/wiki/Xen_Best_Practices >Thanks for the info. It''ll be great if you can point me to the bug / thread for reference. I thought I was following that page, but maybe I made some mistake and the config does not take effect: xen_commandline : placeholder dom0_mem=1G,max:1536M,min:768M,dom0_max_vcpus=6,vpmu=1 If there are any syntax error, shouldn''t it raise error?> -- Pasi >
Pasi Kärkkäinen
2013-Aug-12 08:02 UTC
Re: Free memory reported but not used in new domain creation?
On Mon, Aug 12, 2013 at 03:55:17PM +0800, G.R. wrote:> On Mon, Aug 12, 2013 at 2:15 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote: > > On Mon, Aug 12, 2013 at 01:46:30PM +0800, G.R. wrote: > >> Hi guys, > >> I need your help understanding this behavior: > >> > >> My host has 8GB RAM installed. Xen reports about 1.8G free memory with > >> three domains running. > >> > >> xl info|grep memory > >> total_memory : 7887 > >> free_memory : 1833 > >> > >> xl list > >> Name ID Mem VCPUs State Time(s) > >> Domain-0 0 768 8 r----- 650.2 > >> nas 1 3072 2 -b---- 704.0 > >> windom 3 2047 4 r----- 520.7 > >> > >> Now, when I tried to launch a forth domain with 1G memory assigned, > >> here is the result: > >> > >> xl list > >> Name ID Mem VCPUs State Time(s) > >> Domain-0 0 380 8 r----- 654.1 > >> nas 1 3072 2 -b---- 706.7 > >> windom 3 2047 4 r----- 529.8 > >> freebsd 5 1024 1 -b---- 0.7 > >> > >> xl info|grep memory > >> total_memory : 7887 > >> free_memory : 1184 > >> > >> As you can see, hypervisor is ballooning memory from dom0 instead of > >> allocating from free_memory. If I increase the guest memory of the new > >> domain to 1.5G or 2G. It simply fails to launch, saying something like > >> dom0 memory is below minimal threshold. > >> > >> This gives me the impression that the free_memory is fake. Is it an > >> expected behavior? > >> What are the remaining 1GB memory for? > >> > >> PS: I''m on the xen 4.3.0 release. > >> > > > > Hello, > > > > This is a long-standing bug in xl. > > The workaround is to disable xl autoballooning.. > > > > http://wiki.xen.org/wiki/Xen_Best_Practices > > > > Thanks for the info. It''ll be great if you can point me to the bug / > thread for reference. >I don''t think there''s a "bug entry" about it, but it has been discussed multiple times here on xen-devel, and multiple people have reported the issue.. So far the response has mainly been "disable autoballoon". But I think it''d be better if it worked out-of-the-box!> I thought I was following that page, but maybe I made some mistake and > the config does not take effect: > > xen_commandline : placeholder > dom0_mem=1G,max:1536M,min:768M,dom0_max_vcpus=6,vpmu=1 > > If there are any syntax error, shouldn''t it raise error? >So you need to set autoballoon=0 in /etc/xen/xl.conf -- Pasi
Konrad Rzeszutek Wilk
2013-Aug-12 12:53 UTC
Re: Free memory reported but not used in new domain creation?
On Mon, Aug 12, 2013 at 03:55:17PM +0800, G.R. wrote:> On Mon, Aug 12, 2013 at 2:15 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote: > > On Mon, Aug 12, 2013 at 01:46:30PM +0800, G.R. wrote: > >> Hi guys, > >> I need your help understanding this behavior: > >> > >> My host has 8GB RAM installed. Xen reports about 1.8G free memory with > >> three domains running. > >> > >> xl info|grep memory > >> total_memory : 7887 > >> free_memory : 1833 > >> > >> xl list > >> Name ID Mem VCPUs State Time(s) > >> Domain-0 0 768 8 r----- 650.2 > >> nas 1 3072 2 -b---- 704.0 > >> windom 3 2047 4 r----- 520.7 > >> > >> Now, when I tried to launch a forth domain with 1G memory assigned, > >> here is the result: > >> > >> xl list > >> Name ID Mem VCPUs State Time(s) > >> Domain-0 0 380 8 r----- 654.1 > >> nas 1 3072 2 -b---- 706.7 > >> windom 3 2047 4 r----- 529.8 > >> freebsd 5 1024 1 -b---- 0.7 > >> > >> xl info|grep memory > >> total_memory : 7887 > >> free_memory : 1184 > >> > >> As you can see, hypervisor is ballooning memory from dom0 instead of > >> allocating from free_memory. If I increase the guest memory of the new > >> domain to 1.5G or 2G. It simply fails to launch, saying something like > >> dom0 memory is below minimal threshold. > >> > >> This gives me the impression that the free_memory is fake. Is it an > >> expected behavior? > >> What are the remaining 1GB memory for? > >> > >> PS: I''m on the xen 4.3.0 release. > >> > > > > Hello, > > > > This is a long-standing bug in xl. > > The workaround is to disable xl autoballooning.. > > > > http://wiki.xen.org/wiki/Xen_Best_Practices > > > > Thanks for the info. It''ll be great if you can point me to the bug / > thread for reference. > > I thought I was following that page, but maybe I made some mistake and > the config does not take effect: > > xen_commandline : placeholder > dom0_mem=1G,max:1536M,min:768M,dom0_max_vcpus=6,vpmu=1You need to use spaces instead of '',''.> > If there are any syntax error, shouldn''t it raise error? > > > -- Pasi > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel