On Mon, Aug 22, 2011 at 09:34:27AM -0400, Andrew Lutomirski wrote: > On Mon, Aug 22, 2011 at 5:53 AM, Ingo Molnar <mi...@kernel.org> wrote: > > > > * H. Peter Anvin <h...@zytor.com> wrote: > > > >> Borislav, > >> > >> We're tracking down an issue with the way system call arguments are > >> handled on 32 bits. We have a solution for SYSENTER but not > >> SYSCALL; fixing SYSCALL "properly" appears to be very difficult at > >> best. > >> > >> So the question is: how much overhead would it be to simply fall > >> back to int $0x80 or some other legacy-style domain crossing > >> instruction for 32-bit system calls on AMD64 processors? We don't > >> ever use SYSCALL in legacy mode, so native i386 kernels are > >> unaffected. > > > > Last i measured INT80 and SYSCALL costs they were pretty close to > > each other on AMD CPUs - closer than on Intel. > > From memory, SYSCALL in 64-bit mode on Sandy Bridge is much faster > than int 0xcc, which is presumably about the same speed as int 0x80. > That's because SYSCALL is blazingly fast (<30 ns for a whole system > call) and int is slower.
Just to make sure I'm grokking this correctly - we want to use int $0x80 only for the SYSCALL variant in __kernel_vsyscall, right? Not for all 32-bit syscalls on a 64-bit kernel. Thanks. -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 ------------------------------------------------------------------------------ uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
