On Wed, Jul 1, 2015 at 9:38 AM, Brown, Len <len.br...@intel.com> wrote: > BTW. I've had a discussion w/ LLNL about their needs, > both for security and performance. For security, as concluded > by this thread, a white list is the only way to go. > I'm thinking a bit-vector of allowed MSR offsets... > For performance, they absolutely can not afford a system call > for every single MSR access.
I'm surprised. On a sane kernel, a syscall is about 120 cycles. Just rdmsr to an unoptimized MSR is probably fifty cycles, I'd guess. Of course, LLNL is probably using NOHZ_FULL, which is currently very, very slow. Work is afoot to fix that. > Here an ioctl to have the > msr driver perform a vector of accesses in a single system > call seems the way to go. I can prototype both of these > using turbostat as the customer. How about preadv? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/