>-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Ulrich Drepper >Sent: Friday, August 03, 2007 2:24 AM >To: Nakajima, Jun >Cc: kvm-devel@lists.sourceforge.net >Subject: Re: [kvm-devel] [PATCH 2/2] Add MSR Bitmap support in VMX > >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >Nakajima, Jun wrote: >>> Looking at the Linux context switch code, it can bang on MSR_FS_BASE >> and >>> MSR_KERNEL_GS_BASE. A high context switch rate between >threads (which >>> use %gs or %fs) can show an improvement with this. Things >like kbuild >>> probably won't as they use single threaded processes. >> >> Right. > >In Linux there is no difference between single- and multi-threaded >processes when it comes to setting up segment registers. Every x86-64 >process uses %fs for TLS and every x86 process uses %gs. There are >always variables accessed this way (errno, for instance). >
I have to say, the benefit form _no_ VMExits on these VMExits are not so obviously, because each context switch invloves a guest CR3 update, then a page fault vmexit is triggered and a shadow handling is involved, which is the major cost of guest context switch. -Xin ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
