On Sat, Feb 21, 2015 at 07:51:34AM -0800, Arjan van de Ven wrote: > >> > >>there's a few others as well that I'm chasing down... > >>.. but the flip side, prior to running ring 3 code, why NOT do fast > >>expedites? > > > >It would be good to have before-and-after measurements of actual > >boot time. Are these numbers available? > > To show the boot time, I'm using the timestamp of the "Write protecting" line, > that's pretty much the last thing we print prior to ring 3 execution.
That's a little sad; we ought to be write-protecting kernel read-only data as *early* as possible. > A kernel with default RCU behavior (inside KVM, only virtual devices) looks > like this: > > [ 0.038724] Write protecting the kernel read-only data: 10240k > > a kernel with expedited RCU (using the command line option, so that I don't > have > to recompile between measurements and thus am completely oranges-to-oranges) > > [ 0.031768] Write protecting the kernel read-only data: 10240k > > which, in percentage, is an 18% improvement. Nice improvement, but that suggests that we're spending far too much time waiting on RCU grace periods at boot time. - Josh Triplett -- 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/
