Hi, I''m trying to run kernel compilations on a VM and my times are better than on the host machine. I''m using the time command, so I''m assuming its bugged. I try to use hwclock, and it spits out nothing. Is there an easy way to determine REAL time in a virtual machine? Thanks, David _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> I''m trying to run kernel compilations on a VM and my times > are better than on the host machine. I''m using the time > command, so I''m assuming its bugged. I try to use hwclock, > and it spits out nothing. Is there an easy way to determine > REAL time in a virtual machine?The elapsed time reported by ''time'' should be accurate. system and user time may not be entirely correct, as the kernel doesn''t really understand that its not running the whole time. hwclock won''t work as the unprivileged guest isn''t authorized to read directly from the hardware clock. ''date'' should work fine. Ian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
You''re right Ian. The timing seems to be correct. I recompiled my Xen kernel in an attempt to optimize it. There must''ve been something enabled that degraded performance on the host but not the VM. The majority of what I changed was removing unused drivers from modules and kernels and enabling himem (4GB). Any ideas on that? Thanks, David -----Original Message----- From: Ian Pratt [mailto:m+Ian.Pratt@cl.cam.ac.uk] Sent: Tuesday, June 07, 2005 4:04 PM To: Wolinsky, David; xen-users@lists.xensource.com Cc: ian.pratt@cl.cam.ac.uk Subject: RE: [Xen-users] Current time> I''m trying to run kernel compilations on a VM and my times are better > than on the host machine. I''m using the time command, so I''m assuming> its bugged. I try to use hwclock, and it spits out nothing. Is there> an easy way to determine REAL time in a virtual machine?The elapsed time reported by ''time'' should be accurate. system and user time may not be entirely correct, as the kernel doesn''t really understand that its not running the whole time. hwclock won''t work as the unprivileged guest isn''t authorized to read directly from the hardware clock. ''date'' should work fine. Ian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> You''re right Ian. The timing seems to be correct. I > recompiled my Xen kernel in an attempt to optimize it. There > must''ve been something enabled that degraded performance on > the host but not the VM. The majority of what I changed was > removing unused drivers from modules and kernels and enabling > himem (4GB). Any ideas on that?Hmm, I don''t know what could have caused that. Enabling highmem 4g only causes a tiny slowdown, measureable only by microbenchmarks. Ian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users