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. --Andy > > Also, most installations are either pure 32-bit or dominantly 64-bit, > the significantly mixed-mode case is dwindling. > > Unifying some more in this area would definitely simplify things ... > > Thanks, > > Ingo > ------------------------------------------------------------------------------ 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
