On Fri, Apr 24, 2015 at 10:50 PM, Andy Lutomirski <l...@amacapital.net> wrote: > On Fri, Apr 24, 2015 at 1:46 PM, Denys Vlasenko >>> This might be way more trouble than it's worth. >> >> Exactly my feeling. What are you trying to save? About four CPU >> cycles of checking %ss != __KERNEL_DS on each switch_to? >> That's not worth bothering about. Your last patch seems to be perfect. > > We'll have to do the write to ss almost every time an AMD CPU sleeps > in a syscall.
Why do you think so? Scheduling from a syscall which decided to block won't require writing to %ss, since in this case %ss isn't NULL. Writing to %ss will happen every time we schedule from an interrupt. With timer interrupt every 1 ms it means scheduling at most ~1000 times per second, if _every_ such interrupt causes task switch. This is still not often enough to worry. -- 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/
